THE 

CONTROL    OF    QUALITY 

IN 
MANUFACTURING 


By 
G.  S.  RADFORD 

/( 

Consulting  Engineer;  Member,  American  Society  of 
Mechanical  Engineers;  Society  of  Naval  Architects  and 
Marine  Engineers;  American  Society  of  Naval  Engineers 


NEW  YORK 

THE  RONALD  PRESS  COMPANY 
1922 


Copyright,  1922,  by 
THE  RONALD  PRESS  COMPANY 


All  Rights  Reserved 


c/ 


To  MY  PARENTS 


520411 


PREFACE 

There  is  an  erroneous  but  wide-spread  belief  that  quality 
and  high  cost  go  hand  in  hand.  The  existence  of  this 
feeling  is  readily  explained,  because  it  is  the  general  prac- 
tice to  advertise  quality  as  something  worth  paying  for. 
From  the  purchaser's  standpoint  this  is  very  true,  but  it 
does  not  follow  by  any  means  that  quality  is  costly  to  pro- 
duce. Very  high-grade  ''quality"  products  are  often  high 
priced,  but  lower  grade  and  less  expensive  articles  also 
possess  their  own  quality  standards. 

In  the  factory,  quality  is  a  costly  thing  to  neglect,  yet  it 
is  the  usual  experience  to  find  a  disproportionate  emphasis 
being  placed  upon  quantity  of  output,  in  the  effort  to  effect 
economies.  Often  this  is  not  so  much  due  to  lack  of  proper 
intent  as  it  is  to  the  failure  to  realize  what  the  quality  ap- 
proach means.  To  establish  and  maintain  definite  and 
sensible  standards  of  quality  requires  care  and  thorough- 
ness. These  are  the  very  things  which  remove  obstacles 
to  production  and  thus  decrease  costs — quite  independently 
of  whether  the  product  is  high  grade  or  low  grade,  high 
priced  or  low  priced. 

In  the  following  pages,  presenting  the  results  of  an  inten- 
sive study  of  quality  in  manufacturing,  it  has  been  the 
intention  to  show  that  the  control  of  quality  is  the  correct 
starting  point  for  economy  (as  well  as  to  obtain  higher 
standards  for  their  own  sake),  since  if  quality  is  under 
positive  and  continuous  control,  increase  of  output  follows 
as  a  by-product  advantage.  Hence  one  of  the  central 
thoughts  of  the  book  is  that  increased  output  and  decreased 
costs  are  more  certainly  attained  when  manufacturing 


vi  PREFACE 

problems  are  approached  with  quality,  instead  of  quan- 
tity, as  the  primary  guide  and  objective. 

It  is  well-nigh  impossible  to  pass  a  store  window,  or  to 
ride  in  a  street  car,  or  to  glance  at  the  pages  of  a  magazine 
without  encountering  the  word  "quality."  Yet  there  is 
no  formal  literature  about  quality  in  manufacturing— 
nearly  all  of  our  attention  having  been  devoted  to  quantity. 
Therefore,  in  constructing  this  book  the  introductory 
chapters,  I  and  II,  discuss  the  general  relationships  of 
quality  to  manufacturing. 

When  it  comes  to  controlling  quality,  inspection  plays 
a  large  part.  Chapters  III  to  XI,  accordingly,  are  intended 
to  insure  a  clear  understanding  of  the  various  forms  of 
inspection.  In  sketching  the  relationship  of  inspection  to 
the  control  of  the  flow  of  work  in  process,  the  idea  of  plan- 
ning with  material  in  physical  form  is  advanced  as  an 
advantageous  extension  of  the  usual  planning  systems. 

With  this  earlier  portion  of  the  book  as  a  foundation, 
Chapter  XII,  et  seq.,  takes  up  definitely  the  relation  of 
measurement  to  quality  and  the  development  of  quality 
standards  in  the  various  types  of  manufacturing,  using  the 
methods  for  controlling  dimensional  quality  as  the  principal 
example.  Dimensional  work  has  been  reduced  to  very  pre- 
cise regulation  in  the  industrial  arts  and  thus  permits  of 
exhaustive  treatment.  Hence  most  of  the  illustrations 
throughout  the  book  are  drawn  from  that  source  as  best 
typifying  the  principles  involved  in  quality  control  generally. 

Among  the  important  characteristics  of  manufactured 
articles  there  are  many  other  qualities  which  as  yet  have 
not  been  brought  to  the  same  perfection  of  control  as  dimen- 
sion. Color,  the  control  of  which  is  just  now  beginning  to 
receive  close  attention  in  many  industries,  is  discussed  as 
typical  of  these  other  qualities. 

The  concluding  chapters  present  the  author's  idea  of  the 


PREFACE  vii 

best  method  of  attack  for  approaching,  and  bringing  under 
control,  any  quality  problem  whatever,  regardless  of  the 
particular  industry  or  the  particular  product  which  may 
happen  to  be  involved. 

Throughout  the  text  a  careful  effort  has  been  made  to 
give  credit  to  the  many  firms  and  individuals  who  have 
supplied  technical  information  and  illustrative  matter. 
Probably  this  book  would  not  have  been  written  if  Mr.  L.  P. 
Alford,  Editor  of  Management  Engineering,  had  not  re- 
quested me  to  do  so,  and  then  assisted  in  its  preparation 
with  his  usual  thoughtful  and  competent  advice.  It  only 
remains  to  be  said  that  doubtless  many  of  the  conclusions 
presented  in  the  subject  matter  were  influenced  by  profes- 
sional conversations  with  several  former  associates.  It  is  a 
pleasant  duty  in  this  connection,  to  express  my  obligation 
especially  to  Messrs.  William  B.  Ferguson,  H.  H.  Pinney, 
D.  G.  Seagrave,  Brigadier-General  John  T.  Thompson, 
U.  S.  A.,  retired,  and  Captain  R.  M.  Watt  (C.  C.)  U.  S.  N., 
formerly  Chief  Constructor  and  Chief  of  the  Bureau  of 
Construction  and  Repair. 

G.  S.  RADFORD 
New  York  City, 
September  i,  1922 


CONTENTS 


CHAPTER  PAGE 

I     INTRODUCTION 3 

The  Changed  Industrial  Demand 

Quality  a  Distinguishing  Characteristic  of  Goods 

Uniformity  the  Essence  of  Quality 

Standardization  Does  Not  Bring  Quality 
^jy-niformity  Requires  Continuous  and  Positive  Control 

Instances  of  Failure  in  Quality  Control 
^Advantages  of  Considering  Quality  at  Outset 
cLmproved  Labor  Relationships 

Testimony 
^"increase  of  Output  and  Decrease  of  Costs 

Carnegie's  Maxim 

Experience  of  War  Time  Manufacturing 
-^J&ontrol  of  Quality  Basic 

The  Quality  Bonus 

Experience  of  The  Shelton  Looms 

Experience  of  the  Armstrong  Cork  Company 

Decreased  Selling  Costs  with  Quality  Goods 

II    THE  APPROACH  TO  QUALITY  CONTROL 25 

The  Starting  Point — Determining  Nature  of  Product 

The  Commercial  Factors — Requirements  of  the  Consumer 

The  Design — Securing  Consumer's  Requirements 

Provision  for  Improving  Design 

Materials 

Processes 

Workmanship 

Operating  Organization  and  Records 

Inspection  an  Essential 

III     INSPECTION — THE  NEED  FOR  INDEPENDENT  SCRUTINY  35 

Maintaining  Standards — Measurement  and  Control 

The  Instrument  for  Measuring  and  Controlling 

Convincing  the  Management 
<^Growing  Importance  of  Inspection 
*-Jnspection  Often  a  Necessity,  Always  an  Economy 
*-Need  of  Intensive  Study  of  Inspection 

Sfudy  of  Theory  Needed 
)        *T  unctions  and  Limits  of  Inspection 

'IV    THE  TYPES  OF  INSPECTION 46 

Conformity  with  Special  Factory  Situation 
-"Material  Inspection 
"Office  Inspection 
Inspection 


x  CONTENTS 

CHAPTER  PAGE 

IV    THE  TYPES  OF  INSPECTION — Continued 

^/Process  Inspection 
yCdvantages  of  Centralized  Inspection 
/Inspection  Combined  with  Remedy  of  Defects 

Use  of  Special  Mechanical  Devices 

The  Amount  or  Quantity  of  Inspection 

The  Danger  of  Becoming  "Fussy" 

Unnecessary  Inspection 

Jhe  Percentage  of  Inspection 
impling — The  Theory 
Safeguards  for  Sampling 
Bother  Economies  in  Inspection 


— V^a 


t   V    THE  INSPECTION  DEPARTMENT  IN  THE  ORGANIZATION.   .      63 

^vital  Importance  of  Inspection 

The  Engineering  Department 

The  Production  Department 

The  Inspection  Department 

A  Parallel  with  Governmental  Organization 
ixfhspection's  Relation  to  Engineering  and  Production 

Purpose  Help — Not  Mere  Criticism 
^The  Real  versus  the  Apparent  Organization 
S  Engineering  and  Inspection 
-'Production  and  Inspection 

VI    INSPECTION'S  CONTRIBUTION  TO  GENERAL  SERVICE  ...       74 

The  Collection  of  Useful  Information 

Trouble  Reports 

The  Inspector's  Sense  of  Responsibility 

A  Typical  Instance 

Reception  of  Trouble  Reports 

Inspection  and  the  Assembling  Department 

Benefits  to  Entire  Factory 

An  Example  of  Selective  Assembly 

The  Custody  of  Work  in  Process 

Stimulus  to  Order  and  Cleanliness 

The  Analysis  of  Work  in  Process — "Good"  and  "Bad" 

Handling  Rejected  Parts 

Quality  as  an  Incentive  to  Production 

The  Individual  Worker's  Interest 

J Interest  in  the  Work  Itself 
Expert  Knowledge — Causes  and  Results 
Interest  in  Quality  versus  Fatigue 
A  Phase  of  a  Major  Problem 

VII    INSPECTION'S  RELATION  TO  PLANNING 95 

The  Flow  of  Work  in  Process 
Uneven  Flow — Disadvantages 
Effects  on  Piece  Work 
Supply  of  Raw  Materials 
Material  in  Process 


CONTENTS  xi 

CHAPTER  PAGE 

VII     INSPECTION'S  RELATION  TO  PLANNING — Continued 

Insuring  a  Continuous  Flow 

Planning  with  the  Material  Itself 

Master  Planning 

The  Operation  Mark  or  Symbol 

Operation  Mark  to  Remain  Unchanged 

The  Operation  Data  Sheet 

Route  Tags 

The  Manufacturing  Schedule 

Allowance  for  Losses  in  Process 

Determining  Quantities  of  Work  in  Flow 

The  Design  of  Space  Assignments  for  Planning  with  Material 

Inspection  and  Dispatching 

VIII    CENTRAL  INSPECTION 115 

The  Most  Advanced  Form  of  Inspection 

Not  Restricted  to  One  Form 

Value  of  Self-Counting  Trays 

The  Two-Bin  System  Extended 

Systematic  Layout  for  Material  in  Process 

Layout  of  Central  Inspection  Crib 

Construction  of  Central  Inspection  Cribs 

An  Adaptation  to  Rough  Work 

The  Resulting  House  Cleaning 

An  Adaptation  to  Close  Work  in  Metal 
I  Aisle  Arrangement 

/  Advantages  of  Several  Centralized  Inspection  Spaces 
/  Standard  Arrangement  Desirable 
v  Summary  of  Advantages 


y 


IX    THE  ORGANIZATION  OF  THE  INSPECTION  DEPARTMENT          139 

-designing  the  Instrument  for  Controlling  Quality 
""The  Development  of  Organization 
-The  Chief  Inspector  ^ 

J-hities  of  the  Inspection  Department 

Work  Related  to  Process  Inspection 

The  Line  Organization 

Special  Value  of  Understudies 

Duties  of  Inspectors 

The  Chief  Inspector's  Staff 

The  Inspection  Department  Personnel 

The  Bench  Inspector 

The  Floor-Inspector 

Salvaging  Native  Ability 

A  Case  in  Point 

Study  the  Individual 

MANAGEMENT  OF  THE  INSPECTION  DEPARTMENT  ....     156 

The  Task 

Co-ordination 

The  Use  of  Conferences 


xil  CONTENTS 

CHAPTER  PAGE 

X    MANAGEMENT  OF  THE  INSPECTION  DEPARTMENT — Continued 

Letters  of  Instructions  and  Advice 

Reduction  of  Turnover  of  Inspection  Force 

Provision  for  Promotion 

Wages 

Piece  Work  in  Inspection 

Working  Hours 

The  Cost  of  Inspection 

Teaching  Inspectors 

Combine  Instructions  with  Staff  Supervision 

Unskilled  Help  in  Inspection 

Female  Labor  for  Inspection  Work 

Women  Inspectors  on  Heavy  Work 

Morale 

XI     INSPECTION  IN  PRACTICE 172 

Type  Varies  with  Individual  Factory 

When  to  Use  Extensive  Inspection 

Inspection  in  Automobile  Plants 

The  Packard  Inspection  Service 

An  Example  of  Former  Practice 

Machine  Tool  Industry 

Small  Precision  Work 

General  Machine  Shop  and  Foundry  Practice 

Special  Qases 

Ratio  of  Inspectors  to  Workers 

XII    QUALITY  CONTROL  IN  PRACTICE    ..':.. 187 

Complexity  of  the  Problem  of  Quality 

The  Shell  Contracts  of  the  American  Locomotive  Company 

Beginning  the  Work 

No  Rejections  After  Delivery 

Shells 

Bullets 

Time  Fuses 

Quality  First — Then  Quantity  Follows 

Liberty  Motors  at  the  Lincoln  Motor  Company 

Remington  Arms  Company — Springfield-Enfield  Rifle  Production 

Quality  Is  the  Road  to  Production 

/  XIII     MEASUREMENT  AND  ERRORS  .    .   .   ,   ,   .   . 210 

The  Evolution  of  Measuring 

The  Selection  of  Characteristic  Qualities  for  Measurement 

Standard  Samples 

Dangers  of  Standard  Samples 

Measurement  by  Comparison  with  a  Standard  Scale 

The  Measuring  Instrument 

Danger  of  Overgraduation 

The  Need  of  a  Final  Check 

The  Choice  of  Instruments 

The  Precision  of  Measurement 

Precision  of  Workmanship 


CONTENTS  xiii 

CHAPTER  PAGE 

XIII  MEASUREMENT  AND  ERRORS — Continued 

The  Theory  of  Errors 

When  Theory  and  Practice  Differ 

The  Chain  of  Inaccuracy 

The  Chain  of  Wear 

The  Cure  for  Errors 

XIV  QUALITY  DEFINED — THE  IDEAL  STANDARD 233 

Characteristic  Qualities  of  Product  Must  Be  Known 

Quality  Varies  Continually 

Development  of  the  Design 

The  Theoretical  Standard 

The  Ideal  Standard 

Progress  Toward  More  Exact  Designs 

Changes  in  Design  Must  Be  Avoided 

When  Improvement  Changes  Should  Be  Made 

Every  Cause  Has  Several  Effects 

Precautions  to  Avoid  Changes 

XV    THE  WORKING  STANDARDS 264 

The  Compromise  in  Setting  Tolerances 

Raw  Material  Standards 

Conditioning  Standards 

Standards  of  Finish 

Standards  of  Dimension  and  Form 

Allowed  Variations  Denned 

Necessary  Precautions 

Dimensional  Working  Standards 

Assembling  Standards 

Final  Tests 

Recapitulation 

XVI     REPETITION  MANUFACTURING 264 

Uniformity  for  Economy 

Uniformity  of  Product  Means  Uniformity  Throughout  Production 

Interchangeable  Manufacturing 

The  Industrial  Revolution 

The  Mechanical  Revolution 

Economy  in  Assembling 

The  Work  of  Simeon  North  and  Eli  Whitney 

Continuous  Standardized  Production 

Vital  Importance  of  Uniform  Quality  in  Raw  Materials 

Continuous  Processing 

Duplicate  Manufacturing 

Partial  Interchangeability 

Production  of  Machine  Tools 

The  General  Prniciple 

XVII  THE  DIMENSIONAL  CONTROL  LABORATORY 281 

Practical  Value  of  Precision 
The  Laboratory  Proper 


xiv  CONTENTS 

CHAPTER  PAGE 

XVII    THE  DIMENSIONAL  CONTROL  LABORATORY — Continued 

The  Surface  Plate 

The  Dimensional  "Court  of  Highest  Appeal" 

The  Brown  and  Sharpe  Measuring  Machine 

The  Pratt  and  Whitney  Standard  Measuring  Machine 

The  Johansson  or  Swedish  Block  Gages 

The  Pratt  and  Whitney  Precision  Gages 

Comparators 

Miscellaneous  Equipment 

Personnel 

XVIII    GAGES  AND  GAGE-CHECKING 303 

When  Should  Fixed  Dimension  Gages  Be  Used? 

Fixed-Dimension  Limit  Gages 

Adjustable  Limit  Gages 

Multiplying  Gages 

Special  Gages 

Gage  Tolerances 

The  Application  of  Gages 

Gage-Checking 

The  Slip  in  Transferring  Size 

XIX    THREAD-GAGING 317 

Evolution  of  Thread-Gaging 

Inter-relation  of  Thread  Elements 

Working  Thread  Gages 

The  Hartness  Comparator 

Other  Equipment  for  Measuring  Threads 

Thread  Gage  Tolerances 

Precision  Depends  upon  Service  Requirements 

XX    THE  PRECISE  CONTROL  OF  PROCESSES 330 

What  Dimensional  Precision  Is  Practicable? 

Automobile  Experience 

Tables  of  Tolerances 

Precautions  for  Obtaining  Precise  Work 

The  Principle  of  Balance 

The  Effect  of  Finish  on  Accuracy 

Quick  Checks  on  Precision 

XXI    THE  CONTROL  OF  COLOR 346 

Application  of  Measurement  to  Other  Qualities 

Appearance  and  Color 

Standard  Samples 

The  Standard  Color  Card 

Dangers  of  Standard  Samples 

What  Is  Color? 

The  Illuminant 

The  Subject 

The  Eye 

The  Color  Constants 


CONTENTS  xv 

CHAPTER  PAGE 

XXI    THE  CONTROL  OF  COLOR — Continued 

Color  Vision 

Methods  of  Analyzing  Color 

Analysis  By  Primary  Colors 

Instruments  for  Measuring  Color 

The  Spectrophotometer 

The  Monochromatic  Colorimeter 

Auxiliary  Instruments 

Reduction  of  Errors  in  Color  Work 

Standards  of  Appearance 

XXII    THE  SCIENTIFIC  ATTITUDE  OF  MIND  AND  ITS  METHODS    368 

Science  and  the  Arts 

Science  and  the  Practical  Man 

Theory  or  Theorists 

The  Engineer  as  Co-ordinator 

The  Scientific  Attitude 

The  Scientific  Method 

The  Place  of  the  Engineer 

XXIII    THE  METHOD  OF  ATTACK  TO  CONTROL  QUALITY  ....     377 

The  Approach  to  the  Problem 

Uniformity  within  Limits 

Getting  the  Facts 

Analysis 

Tripartition  or  Tripartite  Analysis 

Quality  Records 

Using  the  Facts — Synthesis  and  Adjustment 

The  Order  of  Procedure 

Begin  with  the  Product 

Written  Descriptions  of  Processes 

The  Assemblage  of  Processes 

Organization  and  System 

Conclusion 


LIST  OF   ILLUSTRATIONS 


FIGURE  PAGE 

1 .  Full  Set  of  Johansson  Gage  Blocks      1 1 

2.  Time  Fuse  Manufacture  of  the  American  Locomotive  Company  .    .  18 

3.  An  Object  Lesson  in  Quality 22 

4.  A  Common  Method  of  Holding  a  Micrometer  Caliper 28 

5.  Measuring  a  Turned  Piece  in  Lathe 31 

6.  A  Centralized  Inspection  Point  in  the  Lincoln  Motor  Company's 

Plant 37 

7.  Tool  and  Gage  Inspection  at  the  Packard  Motor  Car  Company's 

Factory 42 

8.  Some  of  the  Special  Equipment  of  the  Tool  and  Gage-Checking 

Room — Lincoln  Motor  Company 48 

9.  Inspection  of  9.2-Inch  Shells — American  Locomotive  Company    .    .  51 

10.  Rough  Stock  Inspection — Packard  Motor  Car  Company 58 

11.  Sample  Checking  Room — Packard  Motor  Car  Company 65 

12.  Inspection  Room — Lincoln  Motor  Company 71 

13.  Trouble  Report 76 

14.  Inspection  Form — American  International  Corporation,  Hog  Island  80 

15.  Gear  Inspection — Lincoln  Motor  Company 88 

1 6.  The  Flow  of  Work  in  Process — Shell  Work  of  American  Locomotive 

Company 96 

17.  Operation  Study  Sheet  as  Used  at  the  Bridgeport  Armory  of  the 

Remington  Arms  Company 105 

18.  Operation  Data  Sheet .    .106,107 

19.  Route  Tag — Remington  Arms  Company 108 

20.  From  Forging  to  Finished  Crank-Shaft 118 

21.  A  Wood  Frame  Truck 119 

22.  An  "A"  Frame  Wood  Truck  for  Connecting  Rods 120 

23.  Standard  Steel  Tote  Boxes 121 

24.  Diagram  of  Line  of  Flow  of  Work 123 

25.  Diagrammatic  Shop  Arrangement 124 

26.  Diagram  of  Relative  Size  of  Space  Assignments 125 

27.  Transporting  Rack  for  Rifles — Remington  Armory,  Bridgeport     .    .  126 

28.  Type  Section  of  Central  Inspection  Crib 127 

29.  Floor  Plan  of  Central  Inspection  Crib <.    .    .  128 

30.  Floor  Plan  of  Canvas  Shop 129 

31.  Typical  Modern  SJiop  Floor  Plan 132 

32.  Modern  Shop  Floor  Arranged  for  Central  Inspection 133 

33.  Type  Floor  Plan  of  Central  Inspection  Crib .    .  135 

34.  Type  Arrangement  of  Material  Storage  Point  in  Central  Inspection 

Crib 137 

35.  Organization  Chart — Inspection  Department 145 

36.  Various  Sorts  of  Special  Manufacturing  Gages 15° 

37-  Curve  of  Output  and  Number  of  Men 163 

38.  Prestwich  Fluid  Gage  as  Used  to  Inspect  Piston  Pins 167 

39.  Inspection  Organization  Chart — Packard  Motor  Car  Company    .    .  174 

40.  Inspector's  Tag  Disposing  of  Work — Packard  Motor  Car  Company    .  1 76 

41.  Piston  Ring  Inspection — -Packard  Motor  Car  Company 179 

42.  Inspection  of  Time  Fuse  Parts 183 

43.  Perch  for  Inspecting  Textile  Fabrics — The  Shelton  Looms     ....  185 

44.  Typical  Pages  from  Shop  Instruction  Book 192-196 

xvi 


LIST   OF    ILLUSTRATIONS  xvii 

FIGURE  PAGE 

45.  Work  Table  Layout  and  Operation  List  for  Time  Fuses 198 

46.  Fuse  Body  Inspection  Layout 199 

47.  Special  Gages  for  Bottom  Rings  of  Time  Fuses 202 

48.  Typical  Operation  Sheet — Lincoln  Motor  Company 204 

49.  Typical  Instructions  for  Inspection — Lincoln  Motor  Company  .    .    .  205 

50.  Standards  of  Weight  and  Length  for  the  United  States 216 

51.  Method  of  Using  Hub  Micrometer  Caliper  No.  241 — Brown  and 

Sharpe  Manufacturing  Company 218 

52.  Setting  a  Johansson   Adjustable  Limit  Snap  Gage  by   Means  of 

Johansson  Gage  Blocks      222 

53.  Probability  Curve,  Showing  the  Frequency  of  Occurrence  of  an  Error  228 

54.  Checking  Johansson  Adjustable  Limit  Plug  Gage  with  Gage  Blocks 

Mounted  in  Holder 235 

55.  Use  of  Johansson  Gage  Blocks  and  Sine  Bar  to  Check  Taper  of  a 

Milling  Cutter  Shank 239 

56.  Set-Up  of  Johansson  Blocks  for  Checking  Taper  of  a  Special  Plug 

Gage      241 

57.  Order  for  Change  in  Drawing 246 

58.  Measuring  Diameter  of  Automobile  Piston 253 

59.  Reading  Inside  Micrometers  After  Measuring  Inside  of  Cylinder      .  257 

60.  Measuring  Large  Diameter  of  Piece  in  Grinder 260 

61.  Height  Gage  Used  with  Johansson  Blocks 268 

62.  Set-Up  of  Johansson  Blocks  to  Check  Drill  Jig 273 

63.  Special  Milling  Fixture  Using  Johansson  Gage  Blocks  for  Locating 

Purposes 276 

64.  An  Excellent  Dimensional  Control  Center 282 

65.  Brown  and  Sharpe  Measuring  Machine 288 

66.  Pratt  and  Whitney  Measuring  Machine 290 

67.  Details  of  Measuring  Head — Pratt  and  Whitney  Measuring  Machine  292 

68.  Special  Set  of  Johansson  Block  Gages 297 

69.  American  Amplifying  Gage  Used  with  Swedish  Gage  Blocks      .    .    .  299 

70.  Group  of  Brown  and  Sharpe  Gages 305 

71.  Adjustable  Limit  Snap  Gages — Pratt  and  Whitney  Type 307 

72.  Adjustable  Limit   Plug  Gages  with    Reversible   Ends — Pratt   and 

Whitney  Type 308 

73.  Pratt  and  Whitney  Taper  Gages 315 

74.  An  Exaggerated  Form  of  Stud 320 

75.  Typical  Thread  Gages — Pratt  and  Whitney  Company 322 

76.  Typical  Thread  Gage — Pratt  and  Whitney  Company 323 

77.  General  View  of  Hartness  Screw  Thread  Comparator 324 

78.  Another  General  View  of  Hartness  Screw  Thread  Comparator  .    .    .  324 

79.  The  Work  Holder  and  Projection  Lens  of  Hartness  Screw  Thread 

Comparator 325 

80.  Sketch  of  Drill  Showing  Various  Fits — Johansson 334 

81.  Diagram  of  Limit  System — Shaft  Basis — Johansson 335 

82.  Tolerance  System  (Table)  with  the  Shaft  as  Basis — Johansson  .    .    .  336 

83.  Diagram  of  Limit  System — Hole  Basis — Johansson 337 

84.  Tolerance  System  (Table)  with  the  Hole  as  Basis — Johansson  .    .    .  338 

85.  Chart  for  Spectral  Analysis  of  Color  Showing  Relative  Visibility 

Curve 352 

86.  Chart  for  Spectral  Analysis  of  Color  Showing  Typical  Color  Analyses 

Plotted  as  Curves 357 

87.  Sketch  of  Prism  and  Spectrum 359 

88.  Diagram  of  Spectrophotometer 363 

89.  Precision  Torsion  Balance — Roller-Smith 386 


THE  CONTROL  OF  QUALITY 
IN  MANUFACTURING 


CHAPTER   I 

• 

INTRODUCTION 

The  Changed  Industrial  Demand 

The  years  1919  and  1920  marked  definitely  the  end  of  a 
period  in  manufacturing  and  industry.  It  was  characterized 
by  the  demand  for  "maximum  production,"  for  quantity  or 
volume  of  manufactured  goods.  The  means  and  agencies 
of  production — material,  equipment,  and  labor — were 
planned  and  directed  to  satisfy  this  end.  But  with  the 
close  of  this  period  has  come  a  great  change  which  will 
vitally  affect  industry  and  manufacturing  of  the  present 
and  immediate  future. 

The  new  demand  is  for  effective  unit  production,  that  is, 
a  maximum  useful  and  marketable  output  per  machine,  per 
hour,  per  man.  ' '  Useful,  marketable ' '  production  implies  a 
different  characteristic  from  that  associated  with  mere 
quantity.  This  characteristic  is  quality.  It  is  destined  to 
distinguish  the  great  purpose  in  present  and  future  manu- 
facturing, in'  the  same  way  that  quantity  demand  distin- 
guishes the  period  which  has  closed. 

At  the  outset  it  must  be  recognized  that  both  quantity 
and  quality  are  general  or  "universal"  characteristics  in 
that  they  apply  to  all  manufactured  goods.  The  horizon  of 
quality  is  just  as  broad  as  the  horizon  of  quantity.  This  is 
their  similarity — they  both  belong  to  all  kinds  of  goods  and 
articles.  Quality  belongs  to  those  articles  which  are  in- 
expensive no  less  than  to  those  which  are  costly.  It  is 
closely  associated^ with  usefulness  and  marketable  possibili- 
ties. It  is  a  characteristic  emphasized  again  and  again  in 
advertising  and  sales  literature,  but  has  no  direct  connection 


C&N-tROL  OF  QUALITY 

with  cost  or  selling  price.  A  point  to  note  is  that  whether 
the  article  costs  much  or  little,  quality  and  the  reputation 
for  quality  establish  the  market  which  will  make  possible 
quantity  production  and  its  attendant  advantages. 

Quality  a  Distinguishing  Characteristic  of  Goods 

The  term  "quality,"  as  applied  to  the  products  turned 
out  by  industry,  means  the  characteristic  or  group  or  com- 
bination of  characteristics  which  distinguishes  one  article 
from  another,  or  the  goods  of  one  manufacturer  from  those 
of  his  competitors,  or  one  grade  of  product  from  a  certain 
factory  from  another  grade  turned  out  by  the  same  factory. 
Quality  serves  to  identify  an  article.  It  is  the  character- 
istic which  measures  the  evenness  of  a  specific  grade.  Qual- 
ity is  used  in  this  sense  whenever  we  say  that  the  same 
factory  produces  the  same  article  in  several  different  qual- 
ities, or  that  the  output  of  certain  factories  is  graded 
according  to  quality. 

It  is  evident  that  the  group  or  combination  of  charac- 
teristics which  form  the  quality  of  an  article  includes  such 
elements  as  design,  size,  materials,  workmanship,  and  finish. 
To  consider  some  of  these  elements — so  far  as  size  is  in- 
volved, quality  is  concerned  with  precise  adherence  to  size. 
For  instance,  one  pair  of  shoes  of  a  specified  length  and 
width  must  be  like  another  pair  of  shoes  of  the  same  length 
and  width.  In  this  case  quality  depends  upon  adherence  to 
a  particular  characteristic.  The  same  requirement  holds  in 
regard  to  the  raw  materials  from  which  the  article  is  made 
and  to  the  workmanship  applied  in  the  manufacturing.  A 
manufacturer  to  secure  and  maintain  quality  attains  uni- 
formity or  evenness  in  the  raw  materials  which  enter  his 
product  and  in  the  workmanship  applied.  This  adherence 
to  established  requirements  is  a  major  responsibility  of  the 
manufacturer. 


INTRODUCTION  5 

Uniformity  the  Essence  of  Quality 

The  purchaser's  principal  interest  in  quality  is  that 
evenness  or  uniformity  which  results  when  the  manufac- 
turer adheres  to  his  established  requirements.  No  matter 
when  or  where  the  purchaser  buys  an  article  he  expects  the 
same  definite  and  proper  return  for  his  money,  not  only  at 
the  time  of  purchase  but  through  a  reasonable  period  of  use. 
He  is  justified,  no  doubt,  in  expecting  a  gradual  improve- 
ment from  time  to  time  in  the  quality  of  all  the  articles  which 
he  buys,  but  at  any  one  time  his  chief  expectation,  as  re- 
gards quality,  is  that  it  shall  be  the  same  for  like  articles. 
No  shoe  must  be  either  better  or  worse  than  its  mate.  The 
quality  of  two  pairs  of  the  same  grade  of  shoes,  or  of  ten  or  a 
thousand  pairs  for  that  matter,  must  be  practically  identical. 

The  manufacturer  himself  as  a  purchaser  of  raw  ma- 
terials, supplies,  and  equipment,  views  the  matter  in  the 
same  light,  perhaps  with  even  greater  insistence  upon  uni- 
formity and  evenness  of  grade.  Thus  he  requires  that  all 
lots  of  a  given  kind  of  steel  shall  have  the  same  characteris- 
tics from  lot  to  lot;  and,  as  just  indicated,  the  evenness  of 
characteristics  and  the  degree  of  precision  with  which  they 
are  attained  are  what  determines  quality.  As  a  matter  of 
fact,  the  manufacturer  is  often  more  concerned  with  obtain- 
ing uniformity  in  raw  material  than  he  is  in  getting  an  im- 
proved quality,  because  it  is  easier  to  produce  uniform 
results  from  material  which  is  uniform  to  begin  with,  and 
uniformity  of  product  is  what  he  is  after. 

Standardization  Does  Not  Bring  Quality 

At  this  point  it  is  important  to  realize  that  standardiza- 
tion of  products  or  articles  does  not  of  itself  influence 
quality.  Unfortunately,  these  two  terms  are  frequently 
confused  in  use,  but  they  are  not  synonyms.  One  signifies  a 
characteristic,  the  other  a  process. 


6  THE  CONTROL  OF  QUALITY 

Standardization  in  American  industry  has  been  applied 
in  general  to  the  proportions  of  articles  and  is  frequently 
referred  to  as  ' '  standardization  of  proportionality. ' '  An  ex- 
cellent example  is  the  United  States  standard  screw  thread. 
This  was  adopted  many  years  ago  and  is  generally  used 
throughout  American  industry.  However,  it  is  possible  to 
make  United  States  standard  threads  of  poor  quality,  good 
quality,  or  of  any  intermediate  quality.  If  the  proportions 
are  the  same  throughout  this  range  of  quality,  all  of  the 
screws  would  be  "U.  S.  S."  Another  example,  appreciated 
by  everyone,  is  presented  by  our  railroads.  A  standard  rail- 
road gage  is  almost  universally  used  throughout  the  United 
States,  yet  everyone  has  discovered  that  there  is  no  stand- 
ard in  the  quality  of  these  standard-gage  roadbeds.  That 
is,  while  the  gage  is  standard,  the  quality  of  the  roadbeds 
varies.  The  distance  between  the  rails  is  only  one  of  a 
number  of  elements  which  make  up  the  quality  of  the  road- 
bed itself.  So  far  as  the  gage  is  concerned,  the  requirement 
of  quality  is  attained  when  the  rails  are  maintained  at  the 
standard  distance  apart.  But  the  smoothness  of  the  road- 
bed depends  upon  many  other  things,  which  grouped  to- 
gether give  characteristics  or  quality. 

The  quality  of  an  article,  therefore,  is  made  up  of  a  large 
number  of  characteristics  or  attributes,  some  of  which  may 
be  standardized  for  convenience  or  economy.  It  is  quite 
possible  to  have  two  articles,  both  standard,  which  appear 
alike,  but  whose  quality  differs  essentially.  In  the  case  of 
raw  materials,  ordinary  city  water  undoubtedly  is  handled 
in  greater  bulk  than  any  other  standard  commodity.  When 
collection  and  filtration  are  completed,  the  water  is  said  to 
be  distributed  in  standard  form ;  but  even  then  its  quality 
differs  widely  from  place  to  place  and  from  time  to  time. 
Although  alike  to  all  outward  appearances,  the  water  supply 
in  two  cities  may  be  far  different  in  essential  quality,  be- 


INTRODUCTION  7 

cause  the  ingredients  which  cause  a  quality  difference  are 
usually  incapable  of  detection  by  human  senses.  In  this 
instance  also,  quality  depends  on  the  consumers'  require- 
ments. Thus  water  may  be  satisfactory  for  cooking  but 
not  at  all  satisfactory  for  many  industrial  and  technical 
purposes. 

In  the  case  of  manufactured  articles  the  same  difference 
must  be  recognized  between  standards  and  quality.  Re- 
ferring again  to  shoes  as  an  example,  the  purchasing  public 
requires  footwear  in  a  great  variety  of  sizes  and  kinds,  and 
exact  satisfaction  of  each  individual's  wants  would  result  in 
almost  as  many  kinds  of  shoes  as  there  are  persons.  To 
avoid  making  such  an  indefinite  number  of  varieties  and 
sizes  it  is  necessary  to  standardize  some  of  the  elements 
through  striking  a  compromise.  The  effect  of  this  process 
is  to  create  a  sufficient  volume  of  like  work  to  permit  of  using 
the  method  of  quantity  production.  This  compromise  for 
the  purpose  of  securing  the  economy  of  repetition  manu- 
facturing takes  place  when  shoes  are  classified  in  a  stand- 
ardized series  of  styles,  sizes,  and  widths.  A  little  reflection 
will  show  that  this  process  of  compromise  or  standardiza- 
tion is  quite  different  from  the  establishing  of  quality  or 
qualities  which  define  the  character  of  any  particular  make 
and  grade  of  shoe  regardless  of  size  and  of  style. 

Uniformity  Requires  Continuous  and  Positive  Control 

In  meeting  and  satisfying  the  purchaser's  expectations, 
the  manufacturer's  problem  would  be  very  simple  indeed  if 
quality  were  some  definite  thing  which  could  be  easily  and 
accurately  measured  out  so  much  to  an  article — but  it  is 
not.  On  the  contrary,  quality  tends  to  slip  away,  to  change 
and,  in  fact,  be  almost  everything  except  what  it  should  be. 
The  perversity  of  inanimate  things  and  the  fallibility  of 
animate  persons  are  always  at  work  to  render  quality  fugi- 


8  THE  CONTROL  OF  QUALITY 

tive.  In  this  respect  quality  differs  markedly  from  quan- 
tity. It  is  comparatively  easy  to  say  that  we  will  make  a 
thousand  articles  and  to  proceed  to  make  them.  The  prob- 
lem becomes  difficult  only  when  we  are  required  to  make 
them  alike  within  precise  commercial  limits  and  with  mini- 
mum variations  from  standard. 

This  difficulty  in  attaining  uniform  standards  of  quality 
in  manufacturing  makes  the  control  of  quality  so  vitally 
important.  The  advertised  claim  of  quality  is  one  thing  but 
the  positive  and  continuous  control  of  quality  to  definite 
standards  in  the  factory  is  something  altogether  different— 
as  many  people  have  discovered  in  recent  years.  By  "posi- 
tive control  of  quality"  is  meant  that  form  of  manage- 
ment or  direction  which  establishes  the  quality  requirements 
and  then  sets  up  the  organization  and  selects  the  personnel 
capable  of  securing  that  quality.  By  "  continuous  control 
of  quality"  is  meant  the  vigilant  maintenance  and  direction 
of  the  organization  and  personnel  set-up  to  make  the  control 
positive. 

The  resulting  and  final  quality  of  a  manufactured  article 
is  created  and  influenced  by  a  great  number  of  things.  In 
fact  each  element  of  the  business  plays  some  part  in  the 
final  result.  Consequently  the  control  of  quality  must  be 
positive  in  action  in  order  that  all  the  factors  and  agencies 
involved  may  be  co-ordinated.  If  one  factor  gets  out  of 
control,  the  entire  system  is  thrown  out  of  adjustment,  errors 
accumulate,  and  quality  suffers. 

The  control  must  be  continuous  because  quality  is  not 
one  of  those  things  which  once  established  stays  put  for  all 
time.  Its  tendency  to  slip  away  is  incessant.  But  a  single 
serious  slip  in  quality  may  result,  in  some  businesses — for 
example  in  the  manufacture  of  foodstuffs — in  the  destruc- 
tion overnight  of  a  good-will  which  has  required  years  to 
build  up. 


INTRODUCTION  9 

Instance  of  Failure  in  Quality  Control 

In  most  successful  and  long-established  industries  it  has 
become  a  fixed  habit  to  consider  quality  as  basically  neces- 
sary and  thus  to  take  it  for  granted.  Most  of  these  people 
sincerely  believe  that  they  have  quality  under  control,  and 
that  once  having  attained  a  certain  standard  nothing  more 
is  necessary  to  perpetuate  it  indefinitely.  Not  long  ago  an 
engineer  happened  to  spy  a  small  sewing  machine  in  the 
window  of  a  Fifth  Avenue  store.  It  was  of  a  standard  make 
and  therefore  presumably  of  standard  quality.  It  hap- 
pened that  he  had  a  place  where  such  a  machine  might  be 
used  advantageously  so  he  purchased  one,  which  was  handed 
to  him  in  the  original  container.  Upon  trial,  however,  the 
machine  proved  to  be  very  stiff  and  jerky  in  its  action.  So 
he  personally  took  it  back  to  the  store  and  was  informed 
that  such  a  thing  could  not  be. 

"Every  one  of  our  machines  is  inspected  before  it  leaves 
the  factory,  but  you  may  take  it  to  Miss  X  at  the  repair 
desk  in  the  rear. "  Miss  X  took  one  look  at  the  machine  and 
said,  "  Yes,  the  looper  shaft  is  not  straight.  We  get  a  good 
many  that  way.  I'll  give  you  another  one." 

The  second  machine  proved  to  foe  only  a  little  better  than 
the  first.  By  this  time  the  engineer  was  interested  in  the 
problem  as  an  engineer,  so  he  proceeded  to  take  the  ma- 
chine apart  and  discovered  that  the  shaft  had  nothing  to  do 
with  the  trouble  but  that  a  slight  filing  and  fitting  of  three 
other  parts  remedied  the  difficulty,  so  that  his  machine 
finally  "ran  like  a  sewing  machine."  He  was  especially  in- 
terested to  note,  however — and  this  is  the  point  of  the  story 
—that  all  of  these  difficulties  should  have  been  corrected 
and  could  easily  have  been  corrected  in  the  manufacturing 
of  the  parts,  with  a  probable  reduction  in  cost  of  assembly. 
This,  it  may  be  noted,  is  quite  aside  from  the  question  of  the 
reflection  on  this  particular  manufacturer's  reputation  for 


10  THE  CONTROL  OF  QUALITY 

quality,  for  it  is  obvious  that  the  engineer  referred  to  is  not 
going  to  buy  a  life-sized  machine  of  that  particular  make 
until  he  has  made  sure  that  other  manufacturers  do  not  mar- 
ket a  more  uniformly  satisfactory  product. 

The  experience  just  recited  is  significant  of  what  happens 
with  many  concerns.  The  manufacturer  in  question  has 
had  a  long-established  reputation  for  a  satisfactory  product 
and  it  would  be  an  extremely  difficult  and  painful  under- 
taking to  make  him  believe  that  his  control  of  quality  had 
slipped  badly  in  this  instance.  He  probably  believes  that 
he  has  always  had  quality  and  consequently  that  he  always 
will  have  it.  He  regards  it  as  a  part  of  his  fixed  assets. 

In  order  to  get  quality  under  proper  control  it  is  necessary 
to  note  that  every  phase  of  the  business  from  designing  to 
shipping  is  involved  and  requires  critical  examination.  It 
is  not  merely  a  matter  for  the  inspection  department  to  take 
care  of.  For  example,  here  is  a  factory  which  sets  up  a 
very  high  standard  of  dimensional  accuracy  on  paper.  The 
plans  call  for  splitting  thousandths  of  an  inch  in  the  manu- 
facturing processes.  It  has  an  elaborate  and  expensive 
inspection  department,  but  it  lacks  the  modern  mechanical 
methods  for  checking  the  accuracy  of  its  measuring  instru- 
ments. It  cannot  possibly  attain  the  dimensional  precision 
called  for  by  the  plans,  because  of  the  failure  to  provide  a 
comparatively  inexpensive  bit  of  apparatus.  Yet  the  people 
in  the  factory  think  that  they  are  doing  remarkably  fine 
work,  while  as  a  matter  of  fact  they  are  only  fooling  them- 
selves. Their  measuring  instruments  read  to  the  precision 
required  but  they  do  not  measure  to  that  precision — which 
is  something  entirely  different — and  there  is  no  positive  way 
of  checking  them  when  they  wear.  In  this  instance,  as  a 
matter  of  interest,  the  management  was  not  even  aware  of 
the  fact  that  their  dimensional  checking  arrangements  were 
deficient  and  antiquated. 


INTRODUCTION 


I  I 


Here  is  another  factory  which  is  in  nearly  the  same  situa- 
tion but  for  a  different  reason.  It  has  all  of  the  apparatus 
and  all  of  the  provisions  for  inspection  that  are  necessary, 
but  the  work  in  process  is  under  such  unsystematic  regula- 
tion that  the  inspectors  are  frequently  unable  to  tell  you 
with  certainty  what  parts  have  been  rejected  for  minor 
defects  and  what  parts  are  satisfactory  and  up  to  standard. 
Disorder  in  the  shops  has  been  carried  over  into  the  quality 
of  the  output. 

These  are  by  no  means  isolated  examples,  nor  are  they 
exceptional  cases. 


Figure  I.     Full  Set  of  Johansson  Gage  Blocks 

Set  No.   i,  consisting  of  81  blocks;  300,000  different  dimensions  are  possible  with  this  set. 

There  are  other  sets,  but  this  is  the  one  most  used  in  America.     Millimeter  sets  are  also  to  be  had. 

All  blocks  are  accurate  to  within  one-hundred-thousandth  of  an  inch  per  inch  of  dimension. 


12  THE  CONTROL  OF  QUALITY 

Advantages  of  Considering  Quality  at  Outset 

The  idea  seems  to  prevail  that,  because  quantity  produc- 
tion has  been  desired,  quantity  itself  is  the  proper  starting 
point  in  attacking  production  problems.  This  idea  is  seem- 
ingly supported  by  the  honest  belief  in  many  industries, 
both  large  and  small,  that  everything  which  should  be  done 
in  regard  to  quality  is  being  done.  As  a  result,  quality  con- 
trol has  been  disregarded  and  the  demand  for  quantity  has 
been  kept  in  the  forefront. 

Now  the  fact  of  the  matter  is  that  in  concentrating  di- 
rectly on  quantity  production  and  hence  taking  quality 
very  much  for  granted  or  treating  it  as  a  secondary  consid- 
eration, we  have  been  overlooking  an  opportunity;  and  the 
oversight  is  costly  in  more  ways  than  one.  This  is  proved 
at  once  if  we  stop  to  consider  the  advantages  which  accrue 
from  approaching  management  problems  with  quality  in- 
stead of  quantity  as  the  primary  criterion.  There  are 
immense  and  as  yet  largely  undeveloped  economies  to  be 
found  when  management  is  critically  scrutinized  from  the 
quality  standpoint.  These  resulting  advantages  are  quite 
apart  from  the  direct  advantage  of  quality  for  its  own  sake, 
since  they  result  in  better  labor  relationships,  increased  out- 
put, and  decreased  costs. 

Improved  Labor  Relationships 

Let  us  consider  the  point  of  labor  relationships.  These 
present  an  ever  and  most  pressing  factory  problem.  The 
moment  you  endeavor  to  get  an  increase  in  output  (which 
is  attacking  the  problem  from  the  standpoint  of  quantity) 
the  question  of  bargaining  enters  and  provides  an  occasion 
for  dispute.  On  the  other  hand,  if  the  workman  is  taught 
to  better  his  product,  and  is  urged  to  be  more  careful,  and 
to  be  sure  that  his  work  is  performed  correctly,  a  common 
meeting  ground  is  provided.  It  is  a  poor  mechanic  indeed 


INTRODUCTION  13 

who  does  not  take  sufficient  interest  in  his  work  to  join  you 
in  improving  the  results  of  his  craftsmanship. 

Suppose  now  for  the  moment  that  this  greater  attention 
to  quality,  requiring  thoroughness  and  attention  to  detail  as 
it  does,  will  result  in  an  actual  increase  in  output  for  the 
same  effort.  I  say  " suppose"  that  it  does,  although  as  a 
matter  of  fact  it  will  be  proved  presently  that  there  is  no 
supposition  about  it.  But  assuming  for  the  moment  that 
more  attention  on  the  part  of  the  workman  to  quality  will 
bring  about  an  increase  in  output,  have  we  not  secured  that 
increase  in  a  much  pleasanter,  more  effective,  and  more 
permanent  way  than  if  we  had  made  a  direct  request  for  in- 
creased production?  It  is  in  every  way  more  satisfactory 
to  discuss  a  factory  problem  on  a  basis  in  which  both  sides 
are  mutually  interested  and  moving  in  a  common  direction 
which  brings  them  closer  together. 

In  order  to  carry  out  such  quality  discussions  intelli- 
gently, the  management  must  be  informed,  and  very 
thoroughly  informed  at  that,  about  the  technical  side  of  the 
business.  Certainly  this  alone  is  a  desirable  thing.  This 
method  of  approach  is  bound  to  lead  into  a  study  of  the 
technical  details  of  the  business,  to  the  mutual  edification 
of  both  management  and  men.  Failures  to  attain  quality 
standards  take  the  form  of  variations  in  the  characteristic 
qualities.  These  errors  in  manufacturing  must  be  listed 
and  evaluated,  and  the  basic  causes  of  the  errors  located  and 
cured,  all  of  which  is  bound  to  be  both  stimulating  and  in- 
tensely interesting.  It  is  about  the  only  sure  basis  for  off- 
setting the  well-recognized  danger  of  the  modern  industrial 
system.  Men  cease  to  be  mere  automatons  when  they 
think  in  this  way  about  their  work. 

It  is  a  fact  that  the  manager  who  strives  to  interest  his 
organization  in  improving  the  quality  of  the  work  done  will 
find  that  the  process  will  work  out  to  be  a  wonderfully  effec- 


14  THE  CONTROL  OF  QUALITY 

tive  co-ordinator.  When  the  men  are  trying  for  better  and 
more  careful  workmanship,  there  is  small  chance  of  those 
disputes  and  arguments  which  so  frequently  arise  when 
pressure  is  applied  for  more  output.  There  is  a  world  of 
difference  between  bargaining  and  appealing  to  the  pride  of 
craftsmanship.  By  the  very  reason  of  his  being  an  artisan 
the  worker  is  interested  in  improving  his  work. 

Testimony 

In  1912,  a  report  was  submitted  to  the  American  Society 
of  Mechanical  Engineers  on  "The  Present  State  of  the  Art 
of  Industrial  Management,"  which  quoted  an  earlier  paper 
by  L.  P.  Alford  and  A.  Hamilton  Church  on  "The  Princi- 
ples of  Management,"1  setting  forth  the  latter  as: 

1.  The  systematic  use  of  experience, 

2.  The  economic  control  of  effort,  and 

3.  The  promotion  of  personal  effectiveness. 

Both  of  these  papers  dwelt  upon  "the  conscious  trans- 
ference of  skill"  (which  necessitates  that  the  management 
must  first  have  the  skill  to  transfer)  as  a  vital  step  in  pro- 
moting the  personal  effectiveness  of  the  worker.  There 
thus  begins  to  appear  an  attitude  toward  management, 
which,  when  translated  into  general  practice,  is  bound  to 
have  a  profound  influence  on  the  labor  situation.  The 
evidence  is  strong  that  managers  are  leaning  more  and  more 
towards  this  point  of  view,  accentuated  by  a  stronger  and 
growing  realization  of  the  value  of  stressing  quality. 

At  the  annual  meeting  of  the  American  Society  of  Me- 
chanical Engineers  in  December  of  1919,  Robert  B.  Wolf 
(then  manager  of  the  Spanish  River  Pulp  and  Paper  Mills, 
Ltd.,  of  Sault  Ste.  Marie,  Ontario)  presented  a  paper  on 
'The  Use  of  Non-Financial  Incentives  in  Industry,"  which 
was  recognized  at  once  as  containing  many  original  and 

American  Machinist,  May  30,  1912,  Vol.  XXXVI,  p.  857. 


INTRODUCTION  15 

thought-provoking  ideas  that  were  widely  discussed.    The 
following  is  taken  from  Mr.  Wolf's  paper: 

Such  records  can  be  grouped  under  three  main  headings:  quan- 
tity records,  quality  records  and  economy  or  cost  records.  Quality 
records  which  occupy  the  middle  position,  are,  perhaps  of  the  great- 
est importance,  for  they  bring  the  individual's  intelligence  to  bear 
upon  the  problem,  and  as  a  consequence,  by  removing  the  obstacles 
to  uniformity  of  quality,  remove  at  the  same  time  the  obstruction  to 
increased  output.  The  creative  power  of  the  human  mind  is,  how- 
ever, not  content  simply  to  produce  the  best  quality  under  existing 
conditions  of  plant  operation.  The  desire  to  create  new  conditions 
for  the  more  highly  specialized  working  out  of  the  natural  laws  of 
the  process  demands  expression,  and  this  expression  at  once  takes 
the  form  of  suggestions  for  improvements  in  mechanical  devices. 

Only  recently  a  paper  was  presented  by  W.  N.  Polakov 
entitled,  "  Making  Work  Fascinating  as  the  First  Step 
Toward  Reduction  of  Waste."2  This  paper  is  carefully 
worked  out  and  will  repay  reading  with  the  general  attitude 
of  mind  which  recognizes  the  great  desirability  of  organizing 
work  "so  that  the  worker's  intelligence  and  his  creative  or 
imitative  instincts  will  be  brought  into  play.  This  requires : 
(i)  analysis  of  jobs  and  processes  to  bring  out  the  interrela- 
tion of  causes  and  effects,  and  (2)  the  education  of  operators 
in  conscious  control  of  these  forces  and  relations  so  that  they 
can  at  will  influence  the  results."  This  quotation  is  indic- 
ative of  Mr.  Polakov's  attitude,  but  the  reader  is  referred 
to  the  original  text  for  a  more  thorough  presentation  of  the 
subject. 

Increase  of  Output  and  Decrease  of  Costs 

Let  us  now  consider  the  effect  which  the  control  of 
quality  produces  in  increasing  output  and  decreasing  costs 
of  manufacturing.  The  statement  has  already  been  made 
that  such  an  increase  in  the  volume  of  production  does  result 

2  Mechanical  Engineering,  Nov.  1921. 


16  THE  CONTROL  OF  QUALITY 

from  the  establishment  of  adequate  quality  control,  and 
that  it  further  results  in  a  decrease  in  the  cost  of  production 
as  well.  This  idea  was  advanced  in  brief  form  in  a  paper 
by  the  author,  published  in  October,  iQiy.3  Time  and  a 
subsequent  study  of  a  number  of  manufacturing  enterprises 
have  only  served  to  strengthen  these  significant  conclusions. 

Before  exploring  the  basis  of  these  conclusions,  it  is  wise 
to  remember  that  quality  of  itself  is  not  a  costly  thing.  For 
example,  one  buys  a  Ford  car,  not  necessarily  because  it  is 
cheap,  but  because  it  is  built  to  a  rather  definite  standard  of 
quality  and  the  purchaser  has  every  reasonable  assurance  of 
obtaining  a  known  return  for  his  investment  without  refer- 
ence to  price  or  time.  Although  the  Ford  car  is  compara- 
tively inexpensive,  it  has  definite  quality. 

The  misapprehension  that  quality  is  costly  doubtless 
arises  from  the  fact  that  it  is  used  as  the  chief  inducement 
to  make  people  spend  money.  In  current  use,  moreover, 
the  phrase  "quality  production"  as  distinguished  from 
"quantity  production"  does  not  imply  the  idea  of  manu- 
facturing to  certain  predetermined  standards  of  quality  so 
much  as  it  does  that  the  quality  of  material  and  workman- 
ship is  of  unusually  high  grade. 

From  this  latter  mode  of  thinking  has  arisen  a  wide- 
spread belief  that  quality  is  expensive  and  that  it  is  always 
cheaper  to  make  things  to  a  lower  standard.  So  it  is,  if  we 
are  working  intentionally  to  a  lower  grade  and  definite 
standard ;  but  usually  a  lower  grade  article  implies  indefinite 
and  inaccurate  standards,  poor  material  and  slipshod  work- 
manship, and  little,  if  any,  inspection.  In  such  case  the 
outputs  lower  and  the  work  more  expensive  than  if  the 
thing  were  done  correctly  and  well  in  the  first  place.  It  is 
axiomatic  that  it  is  always  cheaper  to  make  things  right  at 
the  start. 


"The  Control  of  Quality,"  by  G.  S.  Radford,  Engineering  Magazine,  Oct.  1917. 


INTRODUCTION  17 

Carnegie's  Maxim 

One  of  our  greatest  manufacturers  clearly  understood 
that  quality  by  itself  is  not  necessarily  costly,  but  it  is  always 
expensive  to  ignore;  as  the  following  quotation  indicates. 
Almost  everyone  knows  that  the  success  of  Andrew  Carnegie 
was  founded  in  meeting  the  " impossible"  requirements  of 
the  United  States  Navy  Department  for  a  much  higher 
grade  of  steel ;  so  it  is  interesting  at  this  point  to  note  what 
he  has  to  say  relative  to  quality  in  his  "Autobiography" : 

We  were  as  proud  of  our  bridges  as  Carlyle  was  of  the  bridge  his 
father  built  across  the  Annan, — "An  honest  brig"  as  the  great  son 
rightly  said. 

This  policy  is  the  true  secret  of  success.  Uphill  work  it  will  be 
for  a  few  years  until  your  work  is  proven,  but  after  that  it  is  smooth 
sailing.  Instead  of  objecting  to  inspectors,  they  should  be  wel- 
comed by  all  manufacturing  establishments.  .A  high  standard  of 
excellence  is  easily  maintained  and  men  are  educated  in  their  effort 
to  reach  excellence.  I  have  never  known  a  concern  to  make  a  de- 
cided success  that  did  not  do  good,  honest  work,  and  even  in  these 
days  of  the  fiercest  competition,  when  everything  would  seem  to  be 
a  matter  of  price,  there  lies  still  at  the  root  of  great  business  success 
the  very  much  more  important  factor  of  quality.  The  effect  of  at- 
tention to  quality,  upon  every  man  in  the  service,  from  the  presi- 
dent of  the  concern  down  to  the  humblest  laborer,  cannot  be 
overestimated.  And  bearing  on  the  same  question,  clean,  fine  work- 
shops and  tools,  well  kept  yards  and  surroundings,  are  of  much 
greater  importance  than  is  usually  supposed.  "  Somebody  appears 
to  belong  to  these  works"  remarked  one  of  a  party  who  passed 
through  the  works.  He  put  his  finger  there  upon  one  of  the  secrets 
of  success. 

The  surest  foundation  of  a  manufacturing  concern,  is  Quality. 
After  that,  and  a  long  way  after,  comes  Cost. 

Experience  of  War  Time  Manufacturing 

The  analysis  of  enterprises  which  were  intensified  by 
war  conditions  illustrates  the  point  vividly.  It  is  now  more 
generally  realized  that  the  specifications  furnished  for  war 


18 


THE  CONTROL  OF  QUALITY 


INTRODUCTION  19 

material  (unfortunately  for  the  manufacturer)  were  inexact 
in  many  cases,  so  that  great  latitude  existed  for  the  applica- 
tion of  judgment  by  inspectors,  this  being  specially  true  in 
the  case  of  the  earlier  contracts  for  foreign  material.  When 
the  contractor  failed  to  clear  up  all  doubtful  points  affecting 
quality  at  the  start,  and  plunged  boldly  into  large-scale 
manufacturing,  the  resulting  failure  of  the  good  old  methods 
of  quantity  production  came  as  a  distinct  shock  to  both 
engineers  and  manufacturers. 

The  lessons  to  be  drawn  from  these  experiences  are  mani- 
fold, but  close  examination  will  reveal  the  fact  that  the 
manufacturers  who  were  more  careful  in  all  matters  deter- 
mining and  affecting  quality,  reaped  a  greater  harvest  in  the 
end,  although  they  usually  took  longer  to  get  started.  The 
most  clearly  marked  contrast  between  those  who  achieved 
results  and  those  who  did  not  do  so  well  is  to  be  found,  in 
every  case,  in  more  exact  definitions  of  quality  backed  up  by 
an  inspection  service  and  general  control  of  quality  adequate 
for  safeguarding  the  standards  established.  It  is  undoubt- 
edly true,  moreover,  that  when  the  precautions  just  stated 
were  taken  and  when,  in  addition,  a  very  high  grade  of  di- 
mensional accuracy  was  adhered  to,  the  quantity  of  output 
was  astonishing.1  The  fact  that  these  enterprises  dealt 
with  large-scale  interchangeable  manufacturing  in  no  way 
weakens  the  general  applicability  and  truth  of  the  principles 
involved ;  which  serves  to  show  that  the  method  of  planning 
for  large  output  at  low  cost  with  quality  as  the  basic  and 
primary  guide  is  more  than  vindicated  by  the  results. 

Control  of  Quality  Basic 

The  facts  demonstrate  that  when  manufacturing  ar- 
rangements are  made  first  and  primarily  with  the  intention 
of  controlling  manufacturing  to  definite  and  uniform  stand- 

4  Typical  examples  of  war  time  production  successes  are  set  forth  in  Chapter  XII. 


20  THE  CONTROL  OF  QUALITY 

ards  of  quality,  quantity  of  output  will  follow.  Briefly,  if 
we  first  take  care  of  quality,  quantity  will  take  care  of  itself. 

This  does  not  mean  that  there  is  no  need  of  the  various 
modern  devices  for  increasing  and  controlling  production, 
because  all  of  these  things  have  their  place.  What  it  does 
mean,  however,  is  that  quality  should  be  the  basic  guide  and 
that,  like  quantity,  it  is  an  integral  part  of  all  the  manufac- 
turing operations  and  demands  recognition  accordingly. 

In  this  connection  the  effect  of  losses  of  work  in  process 
on  quantity  of  output  alone  is  all  too  frequently  overlooked. 
These  losses  seriously  affect  production  in  a  direct  way,  but 
they  still  more  seriously  slow  down  production,  reduce  out- 
put, and  increase  cost  in  certain  indirect  ways  which  are 
much  less  apparent  and  hence,  by  reason  of  this  obscurity, 
more  difficult  to  detect  and  to  remedy.  A  piece  that  is 
wholly  spoiled  represents  a  loss  of  all  the  work  expended  in 
its  manufacture  up  to  the  point  of  spoilage;  yet,  even  so,  its 
outright  loss  is  frequently  cheaper  than  a  partial  injury 
which  requires  the  attention  of  the  best  men  in  the  shop  to 
repair  the  defect,  while  their  regular  work  meanwhile  is  at  a 
standstill.  In  other  words,  the  generalization  that  it  is 
always  easier  to  do  a  thing  right  in  the  first  place,  holds 
equally  well  in  the  factory. 

The  Quality  Bonus 

As  further  indications  of  the  trend  toward  recognizing 
the  value  of  the  quality  approach,  a  few  cases  may  be  cited 
where  managers  have  had  the  courage  to  go  so  far  as  to 
establish  a  wage  payment  based  definitely  upon  quality. 
Even  when  a  quality  bonus  is  superimposed  upon  a  piece 
work  system  which  contemplates  payment  for  good  work 
only,  the  results  obtained  by  a  separate  payment  for  quality 
have  been  astonishingly  satisfactory.  In  two  instances 
which  were  merely  isolated  mechanical  operations,  where 


INTRODUCTION  21 

the  rejections  were  exceedingly  numerous,  shifting  the  piece 
work  rate  to  a  reward  for  quality  reduced  rejections  to  a 
negligible  amount  almost  overnight.  The  following  exam- 
ples, however,  deal  with  quality  bonus  payments  which  are 
in  effect  on  a  much  greater  scale,  and  which  represent  a  radi- 
cal departure  from  currently  accepted  practice. 

Experience  of  The  Shelton  Looms 

Some  time  ago  The  Shelton  Looms,  under  the  progressive 
control  and  guidance  of  Sidney  Blumenthal,  established  a 
quality  bonus  for  weaving.  This  mill  is  engaged  in  making 
high-grade,  deep-pile  silk  and  woolen  fabrics  and  of  course 
a  great  deal  of  attention  is  paid  to  quality.  At  a  certain 
stage  of  development  the  manufacturing  problem  was  ap- 
proached from  a  new  angle,  and  the  quality  bonus  for  weav- 
ing was  adopted.  The  improvement  in  both  quality  and 
quantity  is  indicated  by  contrasting  the  following  figures  5 
(which  are  for  the  first  quarters  of  the  years  stated) : 

1917  1920 

Number  of  men 1,784  1,645 

Hours   per  week 50^  47^ 

Yardage 107  154 

Quality 73i%  90+  % 

Mr.  Blumenthal  has  been  quick  to  take  advantage  of 
suggestions  for  improving  management  methods  and  to 
follow  them  up  with  care.  Consequently,  it  is  interesting 
to  note  that  he  summarizes  the  experience  of  his  company 
in  the  matter  of  paying  for  quality  by  saying,  "Attention 
to  quality  demands  thoroughness,  and  thoroughness  removes 
the  obstacles  to  production." 

Experience  of  the  Armstrong  Cork  Company 

As  a  further  example  in  the  field  of  wage  payment  based 
primarily  upon  quality,  the  experience  of  the  linoleum  divi- 

5  Furnished  through  the  courtesy  of  L.  DeK.  Hubbard,  Operating  Vice-President,  and 
F.  Stolzenberg,  Mill  Manager  of  The  Shelton  Looms. 


22 


THE  CONTROL  OF  QUALITY 


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Figure  3.     An  Object  Lesson  in  Quality 
Drawn  by  an  employee  of  The  Shelton  Looms. 


INTRODUCTION  23 

sion  of  the  Armstrong  Cork  Company,  Lancaster,  Pennsyl- 
vania, is  equally  interesting.6  As  everyone  knows,  "battle- 
ship linoleum"  is  a  standard  product  of  established  quality, 
and  it  is  natural  that  its  makers  should  view  the  matter  of 
production  with  quality  as  a  guide. 

The  bonus  system  for  quality  production  was  conceived 
and  installed  in  1914,  and  has  been  in  successful  operation 
ever  since.  The  primary  object  of  the  plan  was  to  decrease 
the  quantity  of  seconds  produced  and  at  the  same  time  to 
guard  against  a  decreased  production  per  man.  The  result 
has  been  a  consistent  increase  in  quality  each  year,  so  that 
from  the  early  part  of  1914  to  date  the  increase  in  output 
of  first-quality  goods  is  30  per  cent  greater  than  when  the 
quality  bonus  was  started. 

During  this  period  the  production  per  man  increased 
slightly,  but  this  was  not  one  of  the  motives  for  installing 
the  system.  Since  production  in  this  industry  is  deter- 
mined almost  exclusively  by  the  speed  of  given  machinery, 
the  special  aim  was  to  see  that  the  production  governed 
by  the  speed  of  the  machines  was  not  reduced  by  the  efforts 
of  the  men  to  turn  out  perfect  goods.  This  has  been  suc- 
cessfully accomplished.  In  fact,  during  the  war  period 
when  the  man-efficiency  in  industry  generally  reached  a  very 
low  ebb,  the  experience  of  this  plant  was  the  exact  opposite, 
for  the  efficiency  per  man  throughout  the  various  depart- 
ments increased  perceptibly.  This  experience  under  the 
trying  conditions  of  the  period  in  question  is  a  further  vin- 
dication of  the  managerial  judgment  which  makes  quality 
the  basic  criterion  for  attacking  production  problems. 

Decreased  Selling  Costs  with  Quality  Goods 

The  results  obtained  by  The  Shelton  Looms  and  by  the 
Armstrong  Cork  Company  certainly  warrant  a  wider  study 

6  From  information  supplied  through  the  courtesy  of  John  J.  Evans,  General  Manager. 


24  THE  CONTROL  OF  QUALITY 

and  application  of  quality  payment ;  for,  in  addition  to  im- 
proved quality  itself,  the  resulting  increase  in  production 
means  decreased  costs — both  directly  and  through  the  elimi- 
nation of  various  sorts  of  losses. 

There  is,  moreover,  another  phase  of  lowered  cost  when 
quality  receives  attention,  which  should  not  be  overlooked, 
and  that  is  the  lessened  selling  expense  which  is  a  direct 
result  of  supplying  goods  of  standard  quality.  Such  arti- 
cles sell  themselves  at  the  factory. 

There  is  evidence  on  every  hand  that  the  purchasing- 
public  is  applying  much  finer  and  more  intelligent  discrimi- 
nation in  its  buying.  Even  the  non-technical  press  is  full  of 
advertising  matter  setting  forth  in  detail  the  reasons  why 
the  goods  advertised  possess  the  characteristics  claimed  for 
them.  In  other  words,  the  average  purchaser  is  becoming 
a  better  inspector.  Consequently,  work  which  is  held  to 
standard  is  being  more  and  more  appreciated  and  the  sale  of 
such  merchandise  is  immensely  simplified. 

The  element  of  quality  enters  into  a  number  of  things 
which  are  not  a  part  of  production.  When  the  buyer  realizes 
that  nobody  else's  goods  come  to  him  as  well  packed  or  in 
such  an  economical  form  for  him  to  handle,  it  is  easier  to 
sell  to  him.  So  quality  enters  into  packing.  And  it  is  not 
a  far  extension  of  this  idea  to  say  that  quality  enters  into 
shipping  as  well ;  because  prompt  deliveries  by  the  cheapest 
routes  are  certainly  factors  which  are  influential  in  the  repu- 
tation of  your  goods  almost  as  much  as  the  satisfactory 
quality  of  the  goods.  Also,  quality  in  "service"  generates 
reliance  in  the  firm  which  really  stands  behind  its  goods. 

In  fact,  anything  that  tends  to  control  quality  to  more 
definite  and  satisfactory  standards,  whether  in  the  goods 
themselves  or  in  service  connected  therewith,  increases 
selling  power  just  that  much.  Thus  the  statement  that 
quality  goods  are  sold  at  the  factory  becomes  a  reality. 


CHAPTER  II 
THE  APPROACH  TO  QUALITY  CONTROL 

The  Starting  Point — Determining  Nature  of  Product 

Quality,  being  a  characteristic  or  group  of  characteristics 
of  a  product,  is  intimately  a  part  of  the  product.  There- 
fore, the  only  safe  and  orderly  starting  point  for  any  en- 
deavor to  bring  quality  under  exact  control  is  the  product 
itself.  We  may  be  sure  of  successful  results  if  we  begin  at 
this  point.  This  procedure  differs  radically  from  the  usual 
approach  when  quantity  production  is  sought  directly.  In 
the  latter  method  of  attack  on  the  problems  of  manufactur- 
ing there  is  an  ever-present  tendency  to  begin  with  the  sta- 
tistics of  the  business.  Records  of  past  production,  esti- 
mates of  future  production,  and  calculations  as  to  what 
equipment,  tools,  materials,  and  labor  are  necessary  to  se- 
cure an  increased  quantity  are  brought  to  the  forefront.  It 
is  only  later  that  consideration  is  given,  if  time  permits,  to 
matters  affecting  routing,  processing,  inspection,  and  others. 
Now  the  product  is  a  final  result  of  the  orderly  and  co- 
ordinative  working-out  of  all  these  things.  Each  makes  a 
plus  or  minus  contribution  to  quality.  So  the  control  of 
quality  demands  that  the  quality  standards  be  determined 
first,  and  then  that  all  the  arrangements  for  creating  the 
product  be  so  made  as  to  insure  the  realization  of  these 
standards.  This  means  nothing  less  than  shaping  the  means 
to  produce  the  desired  end,  instead  of  permitting  manufac- 
turing system,  methods,  and  what-not  to  determine  the 
character  of  the  factory  output. 

As  L.  P.  Alford  l  has  frequently  stated  in  his  excellent 

1  Editor  of  Management  Engineering. 

25 


26  THE  CONTROL  OF  QUALITY 

analyses  of  management  problems:  "The  end  of  manufac- 
turing is  the  production  of  goods."  Let  us  select  what  we 
intend  to  make  first,  and  then  take  up  the  processes,  work- 
ing arrangements,  organization,  and  system  necessary  to 
achieve  that  result;  for  it  is  by  the  results  and  not  by  the 
means  that  our  work  is  judged. 

This  procedure  distinctly  stresses  the  fundamental  im- 
portance of  establishing  definitely  the  standards  of  quality 
which  are  to  be  followed,  before  we  can  know  exactly  what 
we  are  trying  to  make;  for  if  there  has  been  found  any  vir- 
tue in  preplanning  for  production,  it  has  been  demonstrated 
that  the  more  completely  we  know  what  we  are  trying  to  do, 
before  we  actually  start  doing  it,  the  more  easily  and  swiftly 
will  the  work  be  carried  out.  It  is  this  wider  idea  of  quality 
which  exactly  describes  the  features  of  a  design  with  which 
we  are  chiefly  concerned. 

The  Commercial  Factors — Requirements  of  the  Consumer 

Quality,  therefore,  as  referred  to  here,  involves  a  very 
definite  specification  of  the  important  characteristics  of  the 
product  which  enable  it  to  fulfil  the  needs  and  demands  of 
the  customer  in  a  satisfactory  manner.  The  customer  re- 
quires that  the  article  be  suitable  for  his  purpose.  That  is, 
it  must  be  reliable,  it  must  be  durable  over  a  period  of  time, 
it  must  be  economical  both  in  first  cost  and  in  operation, 
and  usually  it  must  be  pleasing  to  the  senses  as  well. 

The  Design — Securing  Consumer's  Requirements 

From  the  standpoint  of  the  designer  each  of  the  com- 
mercial factors  is  created  by  the  various  features  of  materials 
of  construction,  shape,  dimension,  finish,  and  so  on;  and  the 
quality  of  the  final  result  is  determined  by  these  as  well  as  by 
the  degree  of  precision  with  which  the  design  standards 
are  realized.  This  involves  processes  and  workmanship. 


THE  APPROACH  TO  QUALITY  CONTROL  27 

Needless  to  say,  the  product  should  be  designed  to  meet  the 
commercial  requirements  as  nearly  as  may  be  consistent 
with  economical  manufacture;  and  in  doing  so  the  manu- 
facturer is  faced  with  the  necessity  for  compromising  in 
almost  every  instance.  To  solve  the  problem  intelligently 
requires  a  knowledge  of  what  we  are  trying  to  produce  and 
why.  The  quality  may  be  anything  we  choose,  but  as  a 
starting  point  a  clear  idea  of  what  we  seek  to  accomplish  is 
fundamental. 

As  an  example  of  this  process,  what  is  so  simple  as  an 
alarm  clock?  Like  all  other  clocks  an  alarm  clock  may  be 
expected  to  keep  reasonably  good  time  over  a  period  of 
time.  That  is  part  of  its  job  as  a  clock.  But  beyond  that 
it  has  a  very  unpleasant  duty  to  perform.  It  should  begin 
with  as  gentle  a  tone  as  possible  and  still  accomplish  its  pur- 
pose with  certainty.  Having  attracted  attention,  the  more 
pleasing  its  appearance  the  less  likelihood  of  trouble.  The 
least  the  manufacturer  can  do  for  an  alarm  clock  is  to  pre- 
pare it  for  this  part  of  its  job,  so  he  gives  it  a  fine  finish  in 
nickel  plate. 

Now  a  certain  manufacturer  took  great  pride  in  the  fact 
that  he  was  making  the  cases  of  his  clocks  out  of  a  high 
grade  of  brass,  but  he  overlooked  for  the  time  being  that  the 
quality  of  the  brass  in  the  case  was  of  no  interest  to  the  pur- 
chaser whatever.  His  real  job  as  manufacturer  was  to 
provide  a  nickel-plated  surface  which  would  stand  ordinary 
alarm  clock  service.  When  he  investigated  the  matter  from 
this  point  of  view  he  discovered  that  a  cheaper  grade  of 
brass  would  take  a  better  nickel  plate  and  hold  it  longer 
than  the  higher  priced  material  he  was  using.  Thus  you 
will  observe  that  the  manufacturer,  having  first  studied  his 
product  from  the  standpoint  of  the  commercial  factors  in- 
volved, learned  what  he  was  trying  to  produce  and  why. 
This  led  him  at  once  to  the  conclusion  that  he  should  carry 


28 


THE  CONTROL  OF  QUALITY 


the  problem  to  the  manufacturer  of  raw  materials,  who  might 
reasonably  be  supposed  to  know  more  about  such  materials 
than  anyone  else,  with  the  direct  result  of  an  improvement 


Figure  4.     A  Common  Method  of  Holding  a  Micrometer  Calipcr 
Courtesy  of  Brown  and  Sharpe  Manufacturing  Company. 

in  quality  accompanied  by  an  actual  economy  in  produc- 
tion. 

We  are  pretty  sure  to  be  on  safe  ground  if  we  understand 
that  quality  requires  accuracy  and  care,  and  that  these 
things  are  less  expensive  than  their  opposites — inaccuracy 


THE  APPROACH  TO  QUALITY  CONTROL        29 

and  carelessness.  Consequently,  if  it  has  been  decided  that 
the  commercial  requirements  of  the  case  call  for  a  low-grade 
product,  let  us  proceed  on  that  basis  but  with  the  determina- 
tion that  the  lower  standards  of  quality  are  just  as  delib- 
erately and  intentionally  selected  as  if  they  were  of  higher 
grade. 

Provision  for  Improving  Design 

As  has  been  pointed  out,  economy  of  manufacture  and 
uniformity  of  quality  standards  go  hand  in  hand ;  but  there 
is  no  reason  why  the  standards  should  not  be  raised  from 
time  to  time  without  conflicting  with  the  requirement  of 
uniform  standards  during  any  one  period  or  season  of  manu- 
facturing. One  of  the  desirable  advantages  of  paying 
special  attention  to  quality  is  that  this  method  constantly 
reveals  chances  for  improving  quality  without  increasing 
costs.  The  stage  is  not  likely  to  be  reached  where  further 
advances  are  impracticable. 

The  manufacturer  who  is  satisfied  that  his  product  can- 
not be  improved  is  in  a  dangerous  state  of  mind,  because 
progress  has  not  stopped  in  any  art  or  in  any  science.  If  he 
thinks  that  the  limit  of  improvement  has  been  reached  with 
the  means  available,  then  it  is  time  to  look  for  improved 
methods,  because  no  business  should  stand  still  in  any  sense. 
Ordinarily  when  an  art  is  not  advanced,  the  reason  is  to  be 
found  in  failure  to  provide,  within  the  organization,  for 
systematic  and  progressive  improvement.  Further,  when 
someone  says  that  the  thing  is  impossible,  that  very  thing 
provides  an  opportunity;  for  "the  man  who  says  that  a 
thing  can't  be  done  nowadays,  is  pushed  out  of  the  way  by 
someone  doing  it!" 

From  the  design  standpoint,  the  best  way  to  provide  for 
the  systematic  advance  of  quality,  is  to  realize  at  the  start 
just  what  the  departures  from  the  highest  standard  are  going 


30  THE  CONTROL  OF  QUALITY 

to  be.  Picture  a  lower  grade  product  from  the  viewpoint  of 
a  de-graded  high-grade  article,  in  which  the  reductions  in 
quality  are  known  and  have  been  made  deliberately  and 
with  "malice  aforethought."  Then  we  are  in  a  position  to 
know  the  directions  in  which  improvements  can  be  made, 
and  in  great  detail. 

The  path  of  future  progress  is  thus  made  clear,  and  it 
will  be  found  that  the  process  of  gradually  refining  and  im- 
proving the  product,  step  by  step,  will  bear  fruit  presently 
and  quite  rapidly. 

Materials 

After  the  product  has  been  thoroughly  analyzed  with 
reference  to  the  qualities  which  it  is  desired  to  secure,  and 
after  the  design  has  been  carried  through  the  stages  of  com- 
promise made  necessary  by  considerations  of  economy,  the 
next  step  is  the  selection  of  materials  of  construction.  Now 
the  raw  material  of  one  manufacturer  is  the  finished  product 
of  another.  The  manufacturer  of  the  raw  material  has  been 
through  the  same  process  of  analysis  and  economical  com- 
promise. Hence  it  is  not  reasonable  nor  even  possible  to 
select  materials  which  are  100  per  cent  right  for  our  purposes, 
and  we  are  faced  again  with  the  necessity  for  making  up  our 
minds.  In  fact  this  is  just  one  step  in  a  long  series  of  com- 
promises, all  flowing  from  the  fact  that  quality  is  something 
which  is  peculiarly  subject  to  change  and  variation. 

Since  uniformity  of  result  is  the  thing  sought,  the  most 
desirable  characteristic  of  the  raw  material,  other  things 
being  equal,  is  uniformity.  Once  more,  cost  becomes  a  sec- 
ondary issue,  within  reasonable  limits  of  course.  In  the 
case  of  brass  for  alarm  clock  cases,  it  was  noted  that  a 
cheaper  brass  took  a  more  permanent  and  uniform  nickel 
plating.  But  the  same  demand  for  uniform  results,  or  for 
ease  and  certainty  of  working  up  the  material  may  justify 


THE  APPROACH  TO  QUALITY  CONTROL        31 

a  higher  cost.  Thus  it  is  currently  reported  that  the  lowest 
priced  automobile  made  today  contains  the  highest  per- 
centage of  alloy  steels,  as  a  matter  of  economy. 

Processes 

With  raw  materials  decided  upon,  the  stage  is  reached 
where  processes  must  be  studied  with  the  same  mental  atti- 
tude. Can  the  processes  and  their  equipment  possibly  pro- 
duce the  results  which  are  desired?  If  not  we  should  cer- 
tainly understand  just  how  they  should  be  changed  to  bring 
the  work  to  our  predetermined  standard,  with  economy. 

It  will  invariably  be  found  that  certain  approximations 
to  the  standard  are  necessary.  In  other  words,  the  con- 


Figure  5.     Measuring  a  Turned  Piece  in  Lathe 

Illustrating  another  correct  way  of  holding  micrometer  caliper.     Courtesy  of  Brown  and  Sharpe 
Manufacturing  Company. 


32  THE  CONTROL  OF  QUALITY 

sideration  of  the  problem  requires  another  compromise  as 
soon  as  the  selection  of  manufacturing  processes  is  made. 
This  fact  holds  true  no  matter  how  sensibly  the  processes 
are  selected  or  how  simple  they  may  be.  Quality  varies, 
and  the  design  must  be  modified  accordingly  to  suit  the 
processing,  by  stating  the  permissible  variations  from 
standard  which  will  be  tolerated.  The  idea  of  tolerances 
and  limits  for  variations  from  standard  thus  enters  the  man- 
ufacturing scheme.  Whatever  the  other  conditions  may 
be,  the  processes  must  be  chosen  to  permit  reasonable 
control  of  the  resulting  work  to  the  degree  of  uniformity 
allowed  by  the  tolerances  in  question. 

Workmanship 

Intimately  associated  with  the  study  of  processes  is  the 
matter  of  workmanship,  which  involves  all  questions  asso- 
ciated directly  or  indirectly  with  the  proper  application  of 
the  machinery  provided  for  production.  It  is  not  infre- 
quently the  case  that  the  foreman  says  his  tools  are  all  right 
because  he  has  personally  used  them  to  make  satisfactory 
articles.  On  the  other  hand,  all  he  has  proved  by  using  the 
tools  himself  is  that  an  expert  workman  can  get  the  results 
with  the  equipment  available.  But  the  only  labor  obtain- 
able for  using  these  tools  may  be  quite  incapable  of  attaining 
equally  satisfactory  results  without  changing  the  tools  or 
without  very  careful  instruction,  or  without  change  in  the 
surrounding  conditions  of  inspection  or  other  means  in  use 
to  safeguard  the  production.  ' '  Transfer  of  skill ' '  and  ' '  the 
promotion  of  personal  effectiveness"  at  once  come  into 
action. 

Operating  Organization  and  Records 

Evidently  this  same  process  of  intensive  investigation  of 
the  manufacturer's  problem  from  the  standpoint  of  quality 


THE  APPROACH  TO  QUALITY  CONTROL  33 

will  now  carry  us  to  the  study  of  the  organization  for  operat- 
ing the  factory  and  finally  to  the  system  of  records  of  per- 
formance, which  are  used  in  controlling  the  organization  in 
a  way  to  result  ultimately  in  production  in  accordance  with 
the  quality  standards  as  set.  It  goes  without  saying  that 
each  and  every  factor  entering  into  the  production  problem 
requires  sufficient  study  to  insure  definite  ideas  as  to  how 
each  of  these  factors  can  be  positively  and  separately  con- 
trolled. When  this  control  goes  into  effect  in  the  qualita- 
tive refinement  of  the  industry,  production  problems  for 
the  most  part  will  be  found  to  have  been  solved  in  the  proc- 
ess, simply  because  quality  is  so  fundamental  in  its  nature 
that  it  requires  a  consideration  of  all  the  factors  involved  in 
the  business. 

Inspection  an  Essential 

If  we  were  starting  a  new  project  the  preliminary  study 
of  quality  which  has  been  outlined  in  the  foregoing  pages 
would  be  made  before  and  during  the  starting  of  the  factory. 
Once  manufacturing  has  begun,  however,  the  same  continued 
investigation  must  be  supplemented  and  assisted  by  some 
sure  method  of  bringing  to  the  surface  information  relative 
to  the  errors  and  failures  to  attain  quality  standards. 

This  is  a  situation  in  which  every  factory  finds  itself. 
The  factory  is  running  along  under  pressure  of  production, 
and  quality  is  always  tending  to  slip  away  from  the  stand- 
ard and  to  get  out  of  control.  Consequently  there  is  an 
urgent  need  to  bring  to  light  immediately,  and  to  evaluate 
the  deviations  from  the  desired  quality,  in  order  that  prompt 
steps  may  be  taken  to  limit  and  correct  them. 

As  an  instrument  for  the  prompt  and  perpetual  analysis 
of  the  quality  situation,  and  thus  for  assisting  in  the  control 
of  quality,  a  proper  inspection  service  is  necessary.  But  to 
render  such  service,  as  well  as  to  carry  out  its  many  other 


34  THE  CONTROL  OF  QUALITY 

important  functions,  the  inspection  department  must  be 
placed  in  a  position  to  act  effectively.  That  is  only  com- 
mon sense.  Yet  the  fact  remains  that  there  is  a  very  general 
failure  to  appreciate  the  possibilities  of  inspection,  although 
war  experience  has  helped  considerably  to  dispel  this  lack 
of  appreciation  for  what  inspection  can  do  if  given  a  chance. 
The  subject  is  one  which  has  received  far  too  little  atten- 
tion from  the  standpoint  of  systematic  study.  There  is 
practically  no  literature  or  philosophy  of  inspection.  In 
view  of  this  situation  let  us  now  examine  some  of  the  various 
characteristic  peculiarities  of  inspection  as  an  introduction 
to  the  further  study  of  quality  and  of  methods  for  the  con- 
trol of  quality. 


CHAPTER  III 

INSPECTION— THE    NEED    FOR    INDEPENDENT 

SCRUTINY 

Maintaining  Standards — Measurement  and  Control 

To  set  up  standards  of  quality,  no  matter  how  thor- 
oughly and  carefully  it  is  done,  is  one  thing;  but  to  realize 
those  standards  in  the  actual  work  in  the  factory  is  quite 
another  thing,  for  the  mere  stating  of  what  is  wanted  will 
not  secure  the  result.  Suppose  that  a  design  has  been 
proved  out  in  a  thoroughly  satisfactory  working  model  or 
that  an  article  is  found  to  be  acceptable  to  the  market; 
that  the  working  standards  have  been  determined  with 
experience  based  on  the  best  practice  and  guided  by  the 
highest  mechanical  engineering  skill ;  that  the  equipment  is 
adequate  and  installed  in  keeping  with  the  requirements  of 
economical  and  high-grade  manufacturing;  and  then  sup- 
pose that  the  factory  is  started  to  operate  with  nearly  all 
work  on  a  piece  rate  or  similar  basis,  with  schedules  of 
desired  daily  output  in  the  hands  of  each  department 
head — in  short,  with  the  usual  great  pressure  for  quantity 
production.  Under  these  circumstances  will  the  product 
measure  up  to  the  working  standards  of  quality  so  carefully 
determined  and  clearly  described?  Certainly  not,  unless 
means  are  provided  for  measuring  the  quality  of  the  work  as 
it  is  made,  together  with  the  necessary  organization  for 
seeing  that  the  work  is  held  to  standard  within  economical 
bounds. 

To  control  quality  so  as  to  realize  the  working  standards 
as  nearly  as  may  be,  requires  both  logical  thinking  and 
masterly  management.  The  seriousness  of  the  task  in- 

35 


36  THE  CONTROL  OF  QUALITY 

creases  rapidly  with  the  degree  of  accuracy  or  grade  of 
quality  required  and  with  the  complexity  of  the  product. 
It  is  made  still  more  difficult  if  the  manufacturing  opera- 
tions are  conducted  on  a  large  scale,  for  this  is  one  of  the 
things  which  becomes  magnified  in  the  large  plant  in  a  ratio 
that  increases  much  more  rapidly  than  does  the  size  of  the 
plant  itself.1  There  are  certain  problems  which  are  solved 
in  the  small  shop  with  comparative  ease,  because  of  the  di- 
rectness with  which  they  can  be  seen  and  the  simplicity 
and  promptness  with  which  they  can  be  handled ;  yet  these 
same  problems  become  serious  difficulties  in  the  large 
plant. 

When  we  are  surrounding  the  work  as  it  flows  through 
the  factory  with  an  environment  that  makes  for  quality 
production,  someone  must  exercise  the  duty  of  viewing 
the  work  closely  and  critically  so  as  to  ascertain  the  quality, 
detect  the  errors,  and  present  them  to  the  attention  of  the 
proper  persons  in  such  a  way  as  to  have  the  work  brought 
up  to  standard.  This  function  of  carefully  scrutinizing  the 
work  as  it  progresses  through  the  various  stages  of  manu- 
facture, and  of  pointing  out  the  unsatisfactory  work,  is  the 
principal  purpose  of  inspection;  and  by  " inspection "  is 
meant  inspection  conducted  as  a  function  of  the  factory 
organization,  and  not  by  some  outside  organization  em- 
ployed by  the  purchaser. 

The  Instrument  for  Measuring  and  Controlling 

One  of  the  first  things  brought  to  light  by  a  study  of  the 
problem  of  measuring  the  quality  of  work  and  establishing 
the  necessary  organization  to  secure  and  maintain  this 
quality  is  the  fact  that  inspection  is,  first,  the  instrument  for 
quality  measurement,  and  second,  that  it  is  a  powerful 
factor  in  quality  control.  It  is  like  the  keystone  of  the  arch. 

1  "Production  as  Affected  by  Size  of  Plant,"  by  G.  S.  Radford,  Management  Engineering, 
Aug.  1921. 


NEED  FOR  INDEPENDENT  SCRUTINY 


37 


38  THE  CONTROL  OF  QUALITY 

You  can  get  along  without  it,  but  the  supporting  false  work 
which  must  be  left  to  take  its  place  is  crude,  clumsy,  less 
effective,  and  more  costly. 

Its  relation  to  quality  is  indicated  by  this  thought. 
Quality  may  be  likened  to  a  globule  of  mercury — it  is  al- 
ways tending  to  slip  away.  You  can  hold  mercury  in  a 
given  position  or  on  a  particular  line  with  a  certain  degree 
of  success  without  resorting  to  control.  In  the  same  way  it 
is  possible  to  secure  quality  of  a  certain  kind  and  degree 
without  inspection,  but  in  the  factories  which  stand  as 
leaders  in  their  respective  lines  there  is  always  a  well- 
developed,  scrupulously  maintained  inspection  service. 

Convincing  the  Management 

Every  chief  inspector  must  first  realize,  with  entire 
conviction,  that  inspection  is  a  necessary  step  in  the  great 
process  of  manufacture.  Then  it  becomes  his  painful  duty 
to  get  this  idea  across  to  the  management.  The  latter  task 
is  usually  difficult.  The  inspector  is  responsible  for  quality 
to  a  very  great  extent;  he  is  the  management's  guardian 
against  spoilage  and  waste;  and  when  quality  slips  he  is 
conveniently  at  hand  to  receive  the  blame.  In  many  plants 
where  his  true  relationship  to  quality  is  not  clearly  under- 
stood, this  latter  "duty"  of  receiving  the  blame  for  errors  in 
work  constitutes  a  large  part  of  his  daily  job. 

That  such  an  attitude  toward  the  inspector  is  untenable 
is  proved  by  a  moment's  reflection  on  the  fact  that  the  in- 
spector never  puts  his  hand  to  the  work  except  to  look  it 
over  or  to  measure  it.  The  inspector  enforces  quality  by 
refusing  to  accept  poor  work,  but  this  act  of  rejection  is 
passive  as  regards  enforcing  the  production  of  good  work. 
The  quality  or  lack  of  it  must  necessarily  be  worked  into  the 
material  by  the  production  department  which  controls 
production  processes.  How  then  can  we  blame  the  in- 


NEED  FOR  INDEPENDENT  SCRUTINY  39 

spector  for  lack  of  quality?  In  this  regard  his  duty  is  com- 
plete when  he  passes  upon  the  quality  characteristics  of  the 
goods  and  reports  his  findings.  It  may  be  noted  parenthet- 
ically that  this  very  fact  is  one  of  the  reasons  why  quality 
cannot  be  placed  under  control  until  every  department  of 
the  factory  has  been  reviewed  from  the  quality  standpoint 
and  brought  into  proper  alignment  and  co-ordination. 

Growing  Importance  of  Inspection 

The  kind  of  inspection,  the  manner  of  its  application, 
and  the  extent  to  which  it  is  used  are  conditioned,  of  course, 
by  the  circumstances  in  each  case.  One  must  first  deter- 
mine what  it  is  desired  to  accomplish  by  inspection  and  then 
consider  the  several  different  ways  in  which  the  desired  re- 
sult may  be  obtained,  always  with  a  view  to  selecting  the 
most  economical  method.  There  is  such  a  thing  as  too 
much  inspection  as  well  as  too  little,  but  a  proper  degree  of 
inspection  is  always  an  economy  because  it  stops  leaks  by 
the  early  detection  of  errors  and  thus  prevents  unnecessary 
loss.  From  a  strictly  business  standpoint  it  is  justified  as  an 
insurance  of  that  part  of  "good-will"  which  is  cultivated 
and  retained  by  the  delivery  of  goods  made  to  a  definite 
standard. 

The  evolution  of  inspection  is  both  interesting  and  il- 
luminating. In  early  factory  practice  (and,  for  that  mat- 
ter, in  many  plants  today)  inspection  involved  merely  look- 
ing at  the  work.  Dimensions  were  scant  or  full.  Then 
through  a  gradual  development,  following  in  step  with  the 
attainment  of  greater  accuracy  in  the  mechanical  arts 
which  was  made  possible  by  more  accurate  measuring  de- 
vices and  better  machinery,  we  began  to  measure  in 
hundreths  of  an  inch,  then  thousandths,  then  ten- thou- 
sandths, and  now  in  hundred-thousandths,  if  necessary. 
Such  progress  in  material  ways  calls  for  adequate  and 


40  THE  CONTROL  OF  QUALITY 

similar  adjustments  in  organization;  but  the  development 
of  an  inspection  force  within  the  factory  organization,  and 
hence  paid  for  by  the  manufacturer,  has  not  kept  pace  with 
the  technique  of  manufacturing  except  in  a  rather  limited 
way. 

The  fact  is  that  inspection  in  the  past  has  been  applied 
in  many  cases  by  the  purchaser,  and  often,  especially  in 
government  work,  in  a  manner  to  give  rise  to  the  feeling  in 
the  manufacturer's  mind  that  inspection  should  be  regarded 
as  a  necessary  evil.  Without  question,  a  purchaser's  in- 
spector can  cause  ruinous  conditions  in  any  factory,  es- 
pecially if  there  is  a  lack  of  practical  control,  and  if  the 
specifications  and  other  data  under  which  the  work  is  being 
performed  are  inexact  or  conflicting. 

Inspection  Often  a  Necessity,  Always  an  Economy 

It  is  generally  recognized  that  it  is  a  paying  proposition 
for  the  large  purchaser  of  materials  to  provide  his  own  in- 
spection force.  Yet  it  is  even  more  to  the  interest  of  the 
manufacturer  to  establish  an  inspection  organization  for 
himself.  He  gains  all  the  advantages  secured  by  the  pur- 
chaser and  many  more  besides  through  his  ability  to  control 
and  direct  the  activities  of  his  own  inspecting  force  into  the 
channels  most  useful  to  him. 

If  you  who  are  neither  an  architect  nor  a  builder  are 
about  to  erect  an  expensive  house  or  construct  a  new  factory 
building,  do  you  inspect  it  yourself  or  do  you  employ  some- 
one who  is  competent?  Of  course  you  adopt  the  latter 
method  and  consider  the  money  expended  for  supervising 
the  inspection  well  spent.  You  do  this  no  matter  how 
trustworthy  or  careful  or  reputable  your  builder  may  be. 
Now  consider  carefully  why  this  expenditure  is  a  good 
business  proposition,  and  then  apply  the  reasoning  to  your 
own  factory.  You  cannot  make  everything  yourself,  nor 


NEED  FOR  INDEPENDENT  SCRUTINY  41 

even  view  it  in  a  cursory  way;  nor  can  your  superintendents 
and  foremen,  for  they  are  occupied  with  many  other  things 
principally  connected  with  human  relations  and  quantity  of 
output.  The  average  workman  himself  is  least  of  all 
concerned  with  safeguarding  the  quality  of  your  product, 
unless  you  make  special  provision  to  keep  his  work  up  to 
standard.  In  many  cases  nowadays,  he  has  not  the  ability, 
of  his  own  motion,  to  furnish  the  result  you  desire.  Thus 
inspection  becomes,  oftentimes,  a  necessity.  In  any  event 
an  inspection  service  properly  adjusted  to  the  needs  of  the 
case,  is  an  economy  as  well. 

Comparatively  few  factories  had  their  own  inspection 
services  prior  to  the  war,  but  many  of  those  operating  under 
war  contracts  were  forced  to  provide  such  service  as  a  mat- 
ter of  protection  and  have  learned  thereby  its  value.  It  is 
to  be  hoped  that  much  of  the  old  and  prejudiced  attitude 
toward  factory  inspection  as  an  expense  to  be  avoided  if 
possible,  has  disappeared;  and  that  there  will  be  realized 
the  large  return  in  both  quality  progress  and  decreased 
costs  which  are  made  possible  only  through  the  applica- 
tion of  a  proper  system  of  factory  inspection,  and  not 
otherwise. 

Need  of  Intensive  Study  of  Inspection 

Inspection,  to  be  sure,  is  only  a  part  of  the  control  of 
quality,  but  it  is  an  essential  part.  For  quality  can  be 
controlled  properly  only  through  a  factory  inspection  serv- 
ice— adequately  organized  and  applied  with  an  apprecia- 
tive understanding  of  the  philosophy  behind  it. 

Inspection  is  being  more  generally  used  than  ever  before/ 
but   is   its  function  thoroughly  understood?     At  present 
there  is  evidence  that  inspection  methods  in  many  plants 
are  being  overhauled  to  meet  the  oncoming  and  more  critical 
demands  of  commerce.     In  some  cases,  inspection  depart- 


THE  CONTROL  OF  QUALITY 


NEED  FOR  INDEPENDENT  SCRUTINY         43 

ments  as  such  are  being  provided  for  the  first  time,  and 
existing  inspection  is  being  brought  into  line  with  the 
best  modern  practice,  for  closer  acquaintance  with  a  good 
inspection  service  is  bound  to  prove  its  sound  business 
value,  not  only  in  raising  quality  but  also  in  lowering  costs 
and  increasing  output. 

In  view  of  this  situation  one  might  expect  to  find  con- 
siderable attention  being  paid  to  the  theory  and  practice  of 
inspection,  but  the  engineering  profession  has  been  slow  to 
give  it  the  same  serious  study  that  it  has  shown  in  other 
lines  of  work.  For  example,  the  last  ten  years  have  wit- 
nessed the  intensive  development  of  a  literature  concerning 
itself,  from  the  standpoint  of  the  engineer-executive,  with 
the  business  of  management  in  all  its  details.  This  litera- 
ture is  full  of  references  to  standards  of  quantity  of  output 
per  man  per  day,  and  contains  countless  methods,  schemes, 
and  devices  for  increasing  output  and  decreasing  cost,  all  by 
the  route  of  laying  stress  primarily  on  quantity.  Much  is 
said  about  how  to  determine  the  proper  standards  for 
quantities  of  output  under  given  conditions.  Much  more 
is  said  about  how  to  attain  these  standards  of  quantity 
through  all  the  varied  means  management  engineering  has 
developed ;  for  while  it  is  a  difficult  task  to  determine  just 
what  the  standard  quantity  of  output  should  be;  by  the 
same  token  it  is  much  more  difficult  to  put  these  standards 
into  effect;  just  as  it  is  harder  to  keep  trains  running  on 
schedule  than  it  is  to  lay  out  the  timetable. 

Study  of  Theory  Needed 

But  with  all  this  intensive  study  of  industry,  how  little 
attention  is  paid  to  the  discussion  of  how  to  fix  upon  and 
realize  standards  of  quality  in  production,  and  the  relation 
of  inspection  to  this  problem!  The  Society  of  Industrial 
Engineers  recently,  and  very  properly,  defined  the  activities 


44  THE  CONTROL  OF  QUALITY 

under  which  candidates  for  membership  shall  qualify.2 
Some  twenty  industrial  subjects  were  listed.  An  examina- 
tion of  the  subjects  so  set  forth  indicates  that  no  mention  is 
made  of  inspection,  and  that  little  if  any  consideration  has 
been  devoted  to  quality  control  in  production — certainly 
nothing  like  the  attention  devoted  to  questions  principally 
affecting  quantity  of  output.  This,  moreover,  is  merely 
typical  of  the  general  professional  attitude,  although  this  is 
not  the  first  time  that  something  has  been  used  practically, 
before  the  underlying  theory  has  been  investigated.  Plan- 
ning was  always  done  in  effect,  but  it  was  not  performed 
with  the  greatest  economy  until  the  engineer  separated  it 
out  of  manufacturing  as  a  whole,  for  individual  and  exhaus- 
tive inquiry. 

Can  we  afford  in  this  instance,  to  neglect  so  important  a 
matter  any  longer,  especially  in  the  face  of  existing  condi- 
tions? The  answer  would  seem  to  be  strongly  in  the  nega- 
tive. The  size  of  modern  inspection  departments  alone 
would  warrant  careful  investigation  of  the  subject.  In 
many  well-established  plants  5  per  cent  of  the  entire  work- 
ing force  is  employed  in  the  inspection  department  and  fre- 
quently the  percentage  is  considerably  higher.  In  many 
cases  it  could  be  made  higher  with  advantage,  until  quality 
is  under  such  control  that  the  amount  of  inspection  can  be 
reduced. 

Further,  the  sphere  of  influence  of  the  inspection  service 
is  far  greater  than  its  numerical  relationship,  for  it  reaches 
into  every  department  and  touches  all  the  detailed  factory 
operations  having  to  do  with  creating  and  maintaining 
quality  standards.  These  facts  alone,  it  is  submitted, 
should  indicate  the  need  for  careful  study  of  the  theory  and 
practice  of  inspection,  by  all  who  have  to  do  with  the 
management  of  industry. 

2  Industrial  Management,  Jan.  1920,  p.  55. 


NEED  FOR  INDEPENDENT  SCRUTINY  45 

Functions  and  Limits  of  Inspection 

If  one  is  going  duck-hunting  it  is  just  as  well  to  take 
along  a  shot  gun,  but  having  the  gun  does  not  mean  that  the 
hunter  will  return  with  a  bag  of  ducks.  Unhappily  this 
truism  holds  for  many  things  besides  duck-hunting  and 
leads  to  frequent  misunderstanding  of  the  inspector's 
function.  It  has  its  limitations  like  everything  else.  Its 
purpose  is  to  measure  quality  and  in  this  and  in  other  ways 
to  assist  in  quality  control ;  but  it  does  not  create  quality. 

In  this  preliminary  study  of  the  need  of  inspection  it 
should  be  noted  finally  that  inspection  itself  is  not  a  fixed 
and  definite  function  or  process  except  as  regards  the  prin- 
ciples which  are  involved.  In  contrast  to  being  fixed,  it  is 
very  flexible  and  may  be  applied  in  many  different  ways. 


CHAPTER  IV 
THE  TYPES   OF   INSPECTION 

Conformity  with  Special  Factory  Situation 

The  factory  is  guided  toward  production  in  accordance 
with  the  working  standards,  by  inspection,  which  measures 
quality,  applies  discriminating  judgment  in  close  cases,  and 
in  short  forms  an  environment  that  continually  sorts  out 
defective  work  while  allowing  satisfactory  work  to  proceed. 
Naturally  the  kind  of  inspection  most  suitable  for  a  particu- 
lar situation  depends  on  the  character  of  the  work,  the 
standards  of  quality,  the  skill  of  the  workmen,  and  similar 
matters  relating  to  the  given  manufacturing  conditions  and 
circumstances.  The  thoroughness  of  inspection  varies 
from  a  casual  viewing  of  samples  taken  at  random  in  the 
shop,  up  to  the  analysis,  testing,  or  careful  measurement  in 
separate  inspection  rooms,  of  each  part  after  each  mechan- 
ical operation.  In  large  plants  engaged  on  high-grade, 
interchangeable  work,  almost  every  one  of  the  many  pos- 
sible kinds  of  inspection  will  be  needed  at  some  stage  in  the 
process  of  manufacture. 

Material  Inspection 

Little  need  be  said  of  the  inspection  of  raw  materials. 
The  development  of  highly  standardized  material  specifica- 
tions has  been  made  possible  through  a  previous  and  pro- 
gressive development  in  applied  physics  and  chemistry. 
The  methods  of  the  physical  and  chemical  laboratories 
which  originated  the  data  for  the  standard  specifications  in 
the  first  place,  are  thus  available  in  turn  for  testing  and 
analyzing  the  materials  themselves.  It  is  most  unusual  to 

46 


THE  TYPES  OF  INSPECTION  47 

find  a  plant  of  even  moderate  capacity  without  some  sort  of 
laboratory  in  which  samples  of  each  lot  of  raw  material 
received  by  the  stores  department  are  carefully  inspected 
before  being  passed  for  issue  to  the  factory. 

A  chemical  works  with  a  single  product  as  simple  and 
cheap  as  silicate  of  soda  has  its  own  laboratory  for  inspecting 
both  raw  materials  and  finished  product.  A  flour  mill  using 
the  method  of  mixtures  to  secure  a  definite  quality  standard, 
measures  in  the  laboratory  the  food  values  of  each  lot  of 
grain,  in  order  to  secure  data  for  the  proper  balancing  of  its 
output.  A  paper  mill  makes  microscopical  examination  of 
fibers.  In  a  great  metal-working  plant  we  find  an  assem- 
blage of  thoroughly  equipped  laboratories — chemical,  physi- 
cal, and  metallurgical.  So  it  goes  throughout  the  great 
range  of  the  arts.  Even  small  shops  may  avail  themselves 
of  facilities  for  inspection  of  materials  by  patronizing  the 
commercial  testing  laboratories  to  be  found  in  every  im- 
portant manufacturing  center. 

When  the  local  conditions  are  such  that  there  seems  to  be 
no  method  or  apparatus  already  in  existence  for  this  im- 
portant work,  the  scientist  should  be  called  upon  to  work 
out  the  problem.  There  is  no  reason  today  why  means 
should  not  be  developed  to  meet  almost  any  requirement  for 
inspecting  and  grading  material. 

Office  Inspection 

It  is  common  practice,  also,  to  provide  an  inspection 
service  in  the  drafting-room,  especially  in  the  tool-designing 
section,  so  that  the  work  of  the  "detailers"  and  other 
subordinate  draftsmen  is  carefully  gone  over  by  the 
" checkers."  It  is  perhaps  not  too  far  from  our  subject  to 
note  that  the  application  of  similar  methods  has  been 
carried  into  large  general  offices  in  the  form  of  an  inspection 
of  outgoing  mail.  When  department  heads  sign  outgoing 


48 


THE  CONTROL  OF  QUALITY 


mail  originating  in  their  departments,  it  is  not  unusual  to 
find  a  further  checking  up,  through  carbon  copies  of  such 
mail  being  sent  to  the  office  of  the  general  manager. 

Tool  Inspection 

Factory  inspection  first  appears  in  the  tool-room.  The 
value  of  a  careful  inspection  of  all  special  tools,  fixtures, 
jigs,  and  gages,  is  quite  evident,  whether  they  are  made  in 
the  factory's  tool-room  or  purchased  outside.  If  the  tools 
are  not  correct,  nothing  is  surer  than  that  the  work  will  not 
be  correct.  As  an  additional  check  on  the  tools,  even  if  the 
work  is  simple,  it  is  good  practice  in  quantity  production  to 
make  an  inspection  of  the  first  piece  (and  the  last)  produced 
by  a  new  machine  tool  set-up.  A  theoretically  correct  tool 


Figure  8.     Some  of  the  Special  Equipment  of  the  Tool-  and  Gage-Checking 
Room — Lincoln  Motor  Company 

West  and  Dodge  lead  tester  and  Shore  scleroscope  in  foreground. 


THE  TYPES  OF  INSPECTION  49 

may  not  produce  correct  work,  due  to  some  peculiar  interre- 
lation between  the  tool  and  the  way  it  is  applied  to  the 
stock.  In  many  cases  this  first-piece  inspection  may  be  per- 
formed by  the  mechanic  who  sets  up  the  machine.  This 
duty  sometimes  falls  to  a  special  inspection  service,  how- 
ever, if  such  a  body  exists. 

The  subsequent  periodic  inspection  of  tools,  and  in  fact 
of  all  manufacturing  equipment,  should  be  provided  for 
systematically,  so  that  nothing  will  be  overlooked,  special 
attention  being  given  to  the  points  where  wear  is  rapid  or 
likely  to  cause  the  most  trouble.  Where  gages  are  in  use,  as 
in  small  interchangeable  work,  or  when  specially  accurate 
measuring  instruments  are  used,  as  on  close  work  of  a  size 
beyond  the  accuracy  of  special  gages  or  of  too  small  a 
quantity  to  justify  the  cost  of  gages,  then,  of  course,  the 
greatest  attention  must  be  given  to  verifying  gages  or  instru- 
ments. The  questions  which  arise  in  gage-checking  involve 
an  individual  practice,  and  therefore  will  be  dealt  with  in  a 
separate  chapter. 

Process  Inspection 

Coming  now  to  the  inspection  of  work  in  process,  the 
first  question  to  decide  is  where  the  inspection  is  to  be  made. 
This  ordinarily  involves  either  choosing  between  two  types 
of  inspection  which  are  fairly  well  known  under  the  respec- 
tive names  of  "floor-inspection"  and  "central  inspection" 
or  using  some  combination  of  the  two  systems.  Floor- 
inspection  means  inspecting  work  at  the  machine  or  near  it, 
while  central  inspection  is  the  term  used  to  designate  the 
system  under  which  the  work  to  be  inspected  is  carried  to 
special  spaces  or  rooms  devoted  entirely  to  inspection 
purposes. 

Central  inspection  involves  the  physical  separation  of 
inspection  from  production,  but  it  may  exist  in  any  one  of 


50  THE  CONTROL  OF  QUALITY 

several  forms.  Convenience  rarely  permits  all  inspection 
to  be  centralized  in  one  place  for  the  entire  factory,  so  that 
the  ordinary  method  of  using  central  inspection  involves 
setting  aside  a  place  for  it  in  one  or  more  convenient  loca- 
tions in  each  shop. 

Floor-inspection  may  vary  from  a  sort  of  patrolling 
supervision  which  scans  the  work  at  the  machines,  up  to  the 
taking  of  very  careful  measurements  and  minutely  scrutiniz- 
ing the  work.  It  begins  to  merge  into  central  inspection 
when  the  inspector  is  furnished  with  a  special  inspection 
bench  or  similar  station  located  near  the  machines  whose 
work  he  inspects.  The  inspection  point  may  be  located  be- 
tween machines  in  the  line  of  flow  of  the  work,  just  as  if  it 
were  a  machine  itself.  If  the  separation  between  inspection 
and  production  is  clearly  denned,  we  have  a  distributed  form 
of  central  inspection.  In  its  most  highly  developed  form 
central  inspection  implies  that  all  of  the  work  of  inspection 
in  a  shop  is  centralized  in  a  separate  place,  usually  a  room  or 
enclosure,  to  which  the  work  is  brought. 

Advantages  of  Centralized  Inspection 

The  most  evident  difference  between  the  two  types  of 
inspection  is  that,  in  one  case  the  inspector  goes  to  the  work, 
while  in  the  other  case  the  work  is  brought  to  the  inspector. 
But  this  apparent  difference  is  by  no  means  the  greatest 
dissimilarity.  Centralized  inspection  has  characteristics 
differing  markedly  in  many  other  and  more  important  ways 
from  inspection  that  is  scattered  by  reason  of  being  done  on 
the  site  of  the  work.  Central  inspection,  in  general,  per- 
mits the  use  of  a  less  degree  of  experience  and  skill  than  floor- 
inspection,  because  the  supervision  of  the  work  of  the 
individual  inspector  is  made  easier.  Frequently  division  of 
the  labor  of  inspection  is  possible,  and  economy  of  inspection 
results. 


THE  TYPES  OF  INSPECTION 


52  THE  CONTROL  OF  QUALITY 

Similarly  the  work  of  inspecting  may  be  performed 
more  thoroughly,  as  there  is  less  likelihood  of  interferences. 
More  important  still,  the  inspector  and  the  producer  are 
not  able  to  "get  together"  to  anything  like  the  extent  pos- 
sible in  floor-inspection.  Accordingly  it  is  much  easier  to 
control  quality  to  definite  standards,  as  well  as  to  obtain 
a  better  control  of  the  flow  of  work  by  means  of  central 
inspection,  as  will  be  indicated  in  more  detail  in  Chap- 
ter VIII. 

Highly  centralized  inspection  is  the  ideal  type,  for  it  is 
the  specialization  of  inspection  carried  to  the  limit.  Its  use 
is  not  justified  when  parts  are  large  or  relatively  few  in 
number,  nor  when  the  production  work  requires  such  skilful 
mechanics  that  detailed  inspection  of  their  work  is  not  re- 
quired. With  massive  work,  of  course,  the  inspection  must 
be  made  at  the  place  where  the  work  is  performed.  As  the 
size  of  the  component  parts  of  the  work  decreases,  and 
transporting  them  becomes  less  difficult,  a  stage  is  reached 
when  central  inspection  in  some  form  is  both  possible  and 
desirable.  For  example,  the  last  or  final  inspection  of  large 
automotive  engine  parts  would  naturally  be  made  in  a 
separate  room  or  space,  through  which  the  parts  in  question 
pass  after  being  finished  in  the  shops  where  they  are  made. 
In  high-grade  work  of  the  same  class  it  is  good  practice  to 
remove  these  parts  to  the  inspection  room  after  each  of  a 
few  operations  in  the  course  of  manufacture.  In  this  case 
the  operations  selected  for  central  inspection  are  those  in 
which  close  and  complex  work  is  performed,  and  whose 
influence  upon  succeeding  operations  may  be  very  serious 
in  accumulating  errors. 

When  many  operations  are  used  in  making  one  part  in 
quantity  it  is  usually  better  to  reinforce  central  inspection 
by  a  floor-inspection  in  sufficient  quantity  to  locate  costly 
errors  more  quickly. 


THE  TYPES  OF  INSPECTION  53 

Inspection  Combined  with  Remedy  of  Defects 

Inspection  takes  another  form  in  many  manufacturing 
processes  where  it  is  expedient  to  merge  it  with  production. 
Ordinarily  this  involves  an  inspection  for  defects  in  combi- 
nation with  the  repair  of  the  defects  by  the  inspector.  In 
the  manufacture  of  fabrics,  for  example,  the  work  may  be 
rerolled  on  perches  under  the  eye  of  an  operator  who  repairs 
broken  threads  and  similar  defects  as  he  finds  them.  A 
very  simple  case  of  allied  nature  is  to  be  found  in  the  testing 
of  tanks,  or  water-tight  compartments  in  ships.  The  por- 
tion of  the  structure  to  be  tested  is  subjected  to  water  pres- 
sure, inspected  for  leaks  and  "weeps,"  and  the  leaking  rivets 
and  seams  caulked. 

Use  of  Special  Mechanical  Devices 

Inspection  of  large  quantities  of  small  pieces  is  some- 
times done  economically  by  the  use  of  special  machines. 
In  this  kind  of  inspection,  the  operation  is  best  considered  as 
a  part  of  the  manufacture  of  the  part.  Strictly  speaking,  of 
course,  no  work  is  done  on  the  part,  inasmuch  as  the  part 
is  not  changed  by  the  process  of  inspection,  although  the 
quality  of  the  factory  output  is  improved  thereby.  The 
making  of  rifle  balls  and  small  cartridge  cases  offers  examples 
of  this  sort.  In  one  plant  rifle  bullets  were  carried  on  an 
endless  belt  (originally  designed  as  a  bean-sorting  machine") 
before  a  number  of  inspectors,  so  that  obviously  defective 
ones  might  be  detected  easily  and  removed  quickly.  Simi- 
larly, cartridge  shells  with  surface  defects  are  more  readily 
located  by  the  use  of  special  machines  which  roll  them  before 
the  inspector's  eyes  in  an  endless  procession.  Scrutiny  is 
made  more  certain  by  mirrors  suitably  placed  in  the  ma- 
chine, to  show  all  parts  of  each  shell  as  it  is  rolled  by.  The 
opportunity  for  making  an  inspection  operation  more  ef- 
fective and  less  costly  is  often  revealed  when  consideration 


54  THE  CONTROL  OF  QUALITY 

is  given  to  developing  mechanical  devices  to  assist  in  the 
work  of  inspection. 

The  Amount  or  Quantity  of  Inspection 

Intimately  associated  with  the  question  as  to  the  kind  of 
inspection  to  be  used,  is  the  determination  of  how  much 
inspection — a  question  that  must  be  settled  in  the  light  of 
economy,  for  evidently  we  should  provide  the  least  inspec- 
tion which  will  accomplish  the  purpose. 

The  necessary  amount  will  vary,  of  course,  with  the  prog- 
ress that  has  been  made  in  the  particular  factory  toward  a 
better  control  of  quality.  If  special  attention  is  paid  to 
quality,  the  amount  of  inspection  can  be  reduced  gradually. 
When  this  has  been  done,  however,  the  inspection  should  be 
reconstituted  before  the  manufacture  of  a  radically  new 
model  is  undertaken,  for  reasons  that  would  not  seem  to  re- 
quire detailing. 

In  the  first  place  it  should  be  realized  that  the  inspection 
department  must  use  judgment — "horse  sense" — without 
that  it  is  only  too  possible  for  the  department  to  tie  the 
factory  up  tight.  The  abuse  of  inspection  through  having 
too  many  inspectors  represents,  of  course,  a  dead  loss  from 
the  direct  cost  of  inspection.  It  is  chiefly  to  be  feared, 
however,  because  of  the  deadening  influence  on  production 
of  the  attempt  to  get  too  large  a  percentage  of  the  work  up 
to  standard.  Incidentally  this  error  will  illustrate  the  value 
of  a  clear  appreciation  of  inspection's  function  in  the  control 
of  quality. 

Quality,  as  we  have  seen,  is  a  variable.  It  is  not  practica- 
ble, therefore,  to  conduct  manufacturing  operations  in  such 
a  way  as  to  produce  nothing  but  good  work,  i.e.,  work  that 
is  in  accordance  with  the  specified  standards.  Inevitably 
there  will  be  some  bad  work.  If  inspection  is  applied  with  a 
view  to  reducing  the  amount  of  bad  work  to  the  absolute 


THE  TYPES  OF  INSPECTION  55 

minimum,  the  effect  will  be  to  slow  down  the  quantity  of 
production  to  such  an  extent  as  to  increase  costs  out  of  all 
proportion  to  the  value  of  the  few  parts  that  might  other- 
wise have  become  scrap.  As  a  matter  of  economy,  to  do  a 
certain  amount  of  unsatisfactory  work  is  practically  neces- 
sary, paradoxical  as  this  might  seem  on  first  thought. 

The  Danger  of  Becoming  "Fussy" 

In  many  cases  where  the  standard  is  difficult  to  set 
exactly,  and  judgment  must  enter  to  a  large  extent,  as  in  the 
case  of  inspecting  for  finish  and  surface  defects,  there  is  a 
fertile  field  for  trouble  of  this  sort.  A  factory  manager,  who 
was  a  man  of  unusually  wide  experience  in  many  lines  of 
interchangeable  manufacturing  and  an  alert  and  discerning 
observer  as  well,  once  said  with  reference  to  a  case  of  this 
sort,  "  If  you  pass  a  hundred  parts  through  the  hands  of  a 
hundred  (or  even  fewer)  inspectors,  not  a  single  part  will 
escape  rejection.  Every  piece  will  be  rejected  by  at  least 
one  inspector." 

This  point  of  view  was  vindicated  soon  afterward  in  the 
following  manner:  A  large  quantity  of  sword  bayonet 
blades  were  rejected  for  the  alleged  defect  of  not  being 
straight,  especially  near  the  pointed  end.  Perfect  straight- 
ness  was,  of  course,  impossible.  The  permissible  variations 
from  perfect  straightness  were  purely  a  matter  of  judgment. 
Inasmuch  as  the  blade  was  flexible,  was  of  variable  thick- 
ness, and  curved  both  lengthwise  and  transversely,  it  had 
not  been  practicable  to  design  a  satisfactory  gage,  or  other 
checking  instrument.  It  should  be  said,  by  the  way,  that  the 
purchaser's  chief  inspector  was  very  competent,  reasonable, 
and  fair  minded.  The  working  inspectors  under  his  super- 
vision were  unusually  well  controlled.  He  had  personally 
examined  several  blades  and  rejected  the  lot  of  several 
thousand.  On  the  manufacturer's  side,  however,  the  same 


56  THE  CONTROL  OF  QUALITY 

blades  had  been  passed  by  a  carefully  trained  corps  of  in- 
spectors who  were  in  the  factory's  employ.  Their  foreman 
had  reinspected  a  quantity  of  these  blades,  and  passed 
them  all. 

Here  was  a  large  plant  running  under  pressure  for  pro- 
duction, with  several  days  output  stalled  in  the  middle  of 
the  road  because  the  purchaser  said  the  work  was  wrong, 
while  the  maker  insisted  that  it  was  right.  The  purchaser, 
of  course,  held  the  whip-hand,  and  it  was  of  no  avail  to  plead 
that  there  was  little  military  or  other  practical  advantage  in 
such  a  degree  of  straightness  as  was  required  for  these 
blades.  The  problem  was  one  of  finding  the  quickest  way 
out  of  an  embarrassing  impasse. 

The  cure  for  the  difficulty,  however,  was  simple.  The 
purchaser's  inspector  was  told  that  the  factory  manage- 
ment felt  the  standard  had  been  stiffened  by  imperceptible 
increments  until  it  had  become  impracticable.  It  was  re- 
quested therefore  that  he  examine  20  blades  which  were 
presented  for  his  inspection,  and  designate  those  that  he 
considered  straight. 

The  20  blades  in  question  were  obtained  in  this  way- 
each  of  five  of  the  company's  best  blade  inspectors  were 
asked  to  select,  from  the  rejected  lot,  10  blades  that  he  knew 
were  straight  and  10  that  he  felt  equally  sure  were  not  quite 
straight.  In  this  way  there  were  then  accumulated  50 
"straight"  blades  and  50  " crooked"  ones.  A  committee 
consisting  of  three  of  the  factory  inspection  department's 
expert  supervisors  then  agreed  upon  10  blades  from  each 
lot  of  50,  and  marked  them  accordingly  with  secret  marks, 
10  as  "straight"  and  10  as  "crooked." 

The  result  was  that  the  purchaser's  chief  inspector 
passed  19  of  the  blades  and  rejected  the  twentieth  for  a 
surface  defect  not  in  any  way  connected  with  straightness. 
Of  course,  he  was  promptly  told  the  whole  story,  and  in  a 


THE  TYPES  OF  INSPECTION  57 

fine  spirit  of  fair  play  he  immediately  ordered  the  entire  lot 
inspected  and  accepted  nearly  all. 

This  episode  is  related  here  because  it  exemplifies  so  clearly 
a  number  of  inspection  phenomena  of  the  sort  that  must  be 
taken  account  of,  in  determining  what  is  to  be  avoided. 

Unnecessary  Inspection 

Another  thing  which  requires  attention  is  the  elimina- 
tion of  unnecessary  inspection.  Many  operations  require 
no  inspection  whatever,  or  else  the  inspection  of  work  after 
a  given  operation  may  cover  also  the  work  of  several  preced- 
ing operations.  Similarly,  and  especially  in  the  case  of 
floor-inspection,  if  the  first  several  parts  inspected  are  found 
to  be  right,  the  inspection  of  the  rest  of  the  lot  may  be 
waived.  The  procedure  is  safer,  however,  if  a  few  of  the 
last  parts  made  are  inspected  in  the  same  way. 

Other  parts  may  be  of  such  minor  importance  and 
slight  cost  as  to  make  it  advisable  to  drop  the  inspection  in 
favor  of  the  more  certain  test  of  their  use  in  the  assembling 
department.  This  is  true  of  most  small  screws  and  similar 
minor  screw  machine  products. 

The  Percentage  of  Inspection 

As  to  the  quantity  or  amount  of  inspection  that  should 
be  used  and  when  it  is  to  be  applied,  a  safe  general  rule  is 
this:  Use  100  per  cent  inspection  (i.e.,  the  inspection  of 
every  piece  in  a  lot  as  regards  all  essential  qualities  of  the 
standard)  when  the  work  done  largely  affects  other  work 
that  is  to  follow,  as  in  the  case  of  drawings,  tool-room  out- 
put, gages,  etc.,  or  when  any  part  may  unduly  affect  the 
integrity  of  the  entire  assembly.  Furthermore,  apply  100 
per  cent  inspection  at  points  where  an  operation  is  subject  to 
serious  errors,  or  when  one  operation  may  control  or  mark- 
edly influence  many  subsequent  operations. 


THE  CONTROL  OF  QUALITY 


THE  TYPES  OF  INSPECTION  59 

Sampling— The  Theory 

If  less  than  100  per  cent  inspection  is  used,  we  are 
brought  to  the  consideration  of  sampling.  For  the  most 
part,  inspection  is  made  possible  economically  by  applying 
the  theory  of  this  method.  This  involves  the  assumption 
that  a  piece  selected  at  random  probably  is  representative 
of  the  rest  of  the  lot,  or  that  a  portion  of  a  quantity  of  some 
substance  probably  is  like  the  remainder.  The  word 
"probably"  here  is  to  be  noted.  It  is  sound  theory  to  as- 
sume that  if  something  happens  under  given  conditions, 
exactly  the  same  thing  always  will  happen  again  under  the 
identical  conditions,  which  is  one  way  of  stating  the  law  of 
similarity  in  nature.  In  manufacturing,  however,  we  are 
not  dealing  with  a  theory,  but  rather  with  a  very  practical 
condition  of  things,  which  is  changing  and  varying  all  the 
time. 

Every  portion  of  an  ingot  of  metal,  for  example,  differs 
from  every  other  portion.  This  is  so  well  recognized  in  the 
inspection  of  raw  materials  that  very  exact  practices  have 
been  evolved  for  taking  samples  or  " drillings"  of  metals 
for  analysis;  also  for  selecting  samples  of  coal  and  similar 
substances. 

No  such  definite  practice  is  practicable  for  sampling  in 
shop  inspection.  The  best  we  can  do  is  to  assume,  in  the 
case  of  first-part  inspection,  that  if  the  first  part  made,  after 
the  tools  are  set  up,  is  satisfactory,  the  following  parts 
probably  will  be  right;  or  to  assume  likewise  that  one  part, 
taken  at  random  from  a  lot  of  the  same  parts,  probably  will 
exemplify  the  condition  of  all  of  them.  This,  however,  is 
not  necessarily  true.  We  should  remember  that  one  of  the 
most  common  fallacies  of  reasoning,  well  known  to  students 
of  logic,  is  that  of  arguing  from  a  special  case  to  a  general 
conclusion. 

In  sampling,  this  fallacy  takes  a  peculiar  form.     You 


60  THE  CONTROL  OF  QUALITY 

may  say  to  yourself,  for  example,  "  This  bolt  which  I  hold  in 
my  hand,  is  well  and  correctly  made.  Therefore  all  the 
bolts  in  the  box  from  which  I  took  this  one  are  correct." 
If,  on  the  other  hand,  it  happens  that  the  bolt  is  not  correct, 
you  are  not  nearly  so  willing  or  quick  to  conclude  that  all 
the  bolts  are  not  correct,  so  you  select  one  or  two  more  from 
the  box;  and  if  they  are  correct,  you  promptly  assume,  as  at 
first,  that  all  the  rest  are  correct,  although  you  are  not  quite 
so  certain. 

Such  optimism  may  perhaps  show  a  commendable  spirit, 
but  the  plain  fact  remains  that  your  conclusion  may  not  be 
true,  although  it  probably  is.  It  is  usually  well  to  give 
everyone  and  everything  the  benefit  of  the  doubt.  It 
might  be  said  when  a  conclusion  based  upon  sampling  is  not 
true,  that  the  case  in  hand  is  exceptional  and  that  "the 
exception  proves  the  rule,"  but  the  inference  is  wrong. 
This  is  a  very  old  expression  in  which  the  word  "proves"  is 
used  in  its  original  sense,  as  in  proving  a  gun.  In  reality  the 
exceptional  case  tests  the  rule. 

Safeguards  for  Sampling 

The  use  of  sampling,  especially  in  important  and  costly 
work,  must  be  surrounded  and  reinforced  with  certain  in- 
dependent safeguards.  This  makes  possible  the  great 
economy  which  sampling  permits,  while  protecting  the 
conclusions  from  most  of  the  probable  errors,  provided  hasty 
deductions  are  avoided. 

Among  such  safeguards  are  the  following: 

1.  Mention  has  been  made  of  the  desirability  of  having 
the  first  and  last  few  parts  from  each  machine  set-up  checked 
by  the  tool-setter  or  taken  to  the  inspector  for  checking. 
This  can  be  extended  by  a  continuous,  random  floor-inspec- 
tion or  patrolling  supervision. 

2.  Parts  may  be  taken  at  random  from  current  product 


THE  TYPES  OF  INSPECTION  6l 

and  tried  by  actual  assembly,  thus  discounting  the  danger 
due  to  the  wait  in  shops  and  in  component  stores. 

3.  Parts  in  stores  may  be  similarly  checked  at  random 
from  time  to  time. 

4.  The  two-bin  principle  should  be  applied  wherever 
work  is  piled  up,  either  in  process,  or  in  stores,  in  order  to 
insure  an  uninterrupted  flow  of  work.     (See  Chapter  VIII.) 

5.  A  sort  of  blind,  double  inspection  can  be  tried  oc- 
casionally, in  order  to  check  a  doubtful  inspection  point,  by 
sending  the  same  parts  through  the  same  inspector  twice 
without  notifying  the  inspector.     The  practice  often  gives 
a  valuable  insight  as  to  what  is  really  going  on. 

6.  Each  day  a  good  part  and  a  reject  may  be  collected  at 
random  at  each  inspection  point  and  carried  to  the  central 
gage-checking  point  for  independent  verifying. 

7.  One  or  two  pieces  may  be  quickly  routed  through  all 
operations,  being  carried  from  machine  to  machine  by  the 
foreman  inspector  so  as  to  discount  the  delays  between 
operations.     As  each  operation  requires,  roughly,  a  day  for 
a  lot  of  parts  to  pass  it,  a  part  requiring  fifty  operations  will 
ordinarily  take  fifty  days  to  pass  through  the  shop.     A 
"quick  routed  test  part"  or  "pilot  part,"  which  can  be  put 
through  in  a  clay,  will  be  found  an  excellent  device  for 
detecting  trouble  under  certain  circumstances. 

Other  Economies  in  Inspection 

The  cost  of  inspection  may  be  reduced  in  a  direct  way  by 
combining  it  with  other  duties,  but  any  work  so  added  to 
the  duties  of  the  inspector  should  preferably  be  of  the  sort 
that  is  best  separated  from  actual  production.  The  excep- 
tion is  in  the  case  of  a  combination  of  inspecting  and  re- 
pairing, as  referred  to  earlier  in  this  chapter. 

It  is  not  unusual  to  have  the  inspector  certify  as  to  the 
amount  of  work  done  by  each  workman  whose  work  he 


62  THE  CONTROL  OF  QUALITY 

inspects.  It  is  believed  that  this  combination  of  duties 
should  be  more  extensively  used,  especially  in  steel  construc- 
tion and  similar  large  outside  work.  The  employment  of 
higher  grade  men  for  both  purposes  is  permitted  by  the 
combination  of  duties. 

In  a  highly  developed  central-inspection  system  the 
counting  of  work  done  is  handled  by  the  inspector  as  a 
matter  of  course.  In  addition,  the  collection  of  useful  in- 
formation, the  custody  of  work  in  process,  dispatching  the 
same,  and  otherwise  assisting  the  shop,  are  all  things  in- 
spection is  specially  suited  to  take  charge  of.  Other  serv- 
ices, more  indirect,  which  may  be  allocated  to  the  inspec- 
tion department  with  profit  will  be  mentioned  later  on. 


CHAPTER  V 

THE  INSPECTION   DEPARTMENT  IN  THE 
ORGANIZATION 

Vital  Importance  of  Inspection 

Effective  use  of  inspection  necessarily  is  predicated  upon 
its  recognition  and  elevation  to  a  point  where  it  is  a  real 
factor  in  management. 

The  importance  of  inspection  should  be  recognized  in  a 
practical  and  concrete  way  by  assigning  to  it  a  place  in  the 
organization  commensurate  with  the  vital  duty  of  safe- 
guarding the  quality  of  the  product,  whatever  that  may 
happen  to  be.  When  this  has  been  done  it  is  possible  to 
give  quality  the  attention  it  deserves.  For  it  seems  beyond 
question  that  the  most  prominent  feature  in  the  progress  of 
factory  practice  in  the  future  should  be  the  greater  and 
more  general  appreciation  of  the  possibilities  of  quality  con- 
trol, the  development  of  refinements  in  its  application,  and 
the  consequent  attainment  of  both  higher  standards  of 
quality  and  greater  fidelity  to  such  standards,  with  a  de- 
cided gain  in  economy. 

The  last  few  years  have  witnessed  the  evolution  of  a 
science  of  management  and  its  translation  into  an  engineer- 
ing practice  covering  planning  in  its  widest  sense,  the  deter- 
mination of  standards  of  output,  and  the  methods  of 
handling  a  complexity  of  human  relations,  rapidly  changing 
under  the  reaction  of  labor  to  the  new  situations  introduced 
into  industry.  The  machinery  thus  created  and  developed 
will  now  be  used  to  accelerate  the  progress  of  industrial 
management,  with  care  for  quality  more  and  more  as  the 
guiding  principle.  It  is  but  in  the  natural  course  of  events 

63 


64  THE  CONTROL  OF  QUALITY 

that  the  greater  mechanical  accuracy  made  more  generally 
possible  through  development  under  stress  of  war  time,  to- 
gether with  the  experience  of  manufacturers  during  that 
period,  will  now  result  in  an  intensive  application  of  these 
new  forces  in  the  betterment  of  the  work  of  the  industrial 
world.  The  reaction  on  labor  alone  will  be  worth  the 
effort.  As  stated ,  this  attitude  on  the  part  of  managers  leads 
toward  better  inspection,  which  in  turn  will  have  to  be  pre- 
ceded by  a  deeper  understanding  of  the  inspection  function. 
Every  student  of  industrial  management  must  recognize 
that  the  late  Dr.  Frederick  W.  Taylor  made  a  remarkably 
clear  and  powerful  analysis  of  the  elements  of  manufactur- 
ing, although  he  may  not  entirely  accept  the  Taylor  methods 
for  handling  the  elements  thus  disclosed.  It  is  therefore 
interesting  to  note  that  Dr.  Taylor's  analysis  of  the  duties 
of  foremen,  even  in  ordinary  machine  shop  practice,  resulted 
in  the  separating  out  of  inspection,  as  a  function  calling  for 
an  independent  foreman.  In  other  words,  he  recognized 
the  necessity  for  an  inspector  or  quality  boss,  just  as  he  pro- 
vided for  a  " speed  boss"  to  look  out  for  quantity,  and  a 
planner  to  do  the  thinking  and  prearranging  necessary  to 
co-ordinate  subsequent  effort.  This  analysis  is  evidence  of 
a  realization  that  someone  should  attend  to  inspection,  and 
that  so  important  a  duty  is  best  carried  out  independently 
and  therefore  with  authority. 

The  Engineering  Department 

Suppose  that  we  analyze  some  great  manufacturing 
enterprise  into  its  most  general  terms.  Our  problem  is  to 
make,  let  us  say,  a  large  number  of  engines,  or  motors,  or 
guns,  or  other  articles  assembled  from  component  parts 
which  must  be  made  to  rather  definite  standards  of  accuracy 
and  finish.  What  the  industry  happens  to  be  makes  little 
difference,  because  all  involve  the  application  of  labor  to  an 


INSPECTION  DEPARTMENT  IN  ORGANIZATION 


66  THE  CONTROL  OF  QUALITY 

assemblage  of  raw  materials.  Perhaps  the  first  large  duty 
or  group  of  duties  that  we  would  segregate  in  our  minds 
would  be  the  engineering  group,  whose  duty  is  to  make  plans 
for  something  that  is  to  be  done  in  the  future,  and  to  con- 
centrate on  the  practical  and  intensive  application  of  an- 
ticipatory imagination. 

This  work  is  warranted  because  it  reduces  the  cost  of 
production  through  describing  exactly  what  is  to  be  done 
and  thus  avoiding  waste  of  effort  on  the  shop's  part  in  doing 
things  that  are  not  wanted.  This  passion  for  visualizing 
work  before  it  is  performed  and  preparing  plans  showing 
what  should  be  done,  is  resulting  in  the  transfer  of  more  and 
more  work  from  the  domain  of  ''trial  and  error"  in  the 
actual  fabrication  of  the  work,  to  its  more  scientific  treat- 
ment in  the  engineering  department.  All  doubtful  ques- 
tions are  settled  as  a  part  of  preparation  for  production  and 
before  the  latter  begins,  and  a  sharp  line  is  drawn  between 
experimental  or  research  work  and  the  business  of  making 
things.  Vexatious  and  costly  delays  are  confined  to  the 
laboratory  and  the  engineering  office  in  order  that  produc- 
tion may  flow  on  without  interruption  from  such  things. 

Thus  the  designing  engineer  works  out  his  plans  on  paper, 
describing  in  great  detail  what  the  shops  are  to  make;  the 
production  engineer  makes  plans  on  paper  covering  the 
things  to  be  done  to  obtain  greater  productive  efficiency, 
and  so  on.  None  of  this  effort  is  expended  in  doing  the 
physical  work  of  production,  but  it  does  result  in  a  much 
greater  output  from  the  whole  organization.  It  pays 
amazingly.  It  is  cheaper  to  correct  mistakes  on  paper 
before  they  have  been  worked  into  steel. 

The  Production  Department 

Continuing  the  analysis  of  manufacturing,  probably  the 
next  great  function  that  will  attract  attention,  if  our  minds 


INSPECTION    DEPARTMENT   IN   ORGANIZATION  67 

are  proceeding  in  an  orderly  manner,  is  that  of  production, 
which  has  the  duty  of  applying  human  effort  to  the  execu- 
tion of  the  plans  made  by  the  engineering  group.  The 
latter's  work  is  now  subjected  to  the  acid  test — it  is  con- 
vertible into  action,  or  it  is  not. 

The  time  element,  it  may  be  noted,  is  significant  here, 
for  production  is  most  seriously  engaged  with  meeting  the 
pressing  necessities  of  the  present,  just  as  engineering  deals 
principally  with  the  future.  Production  solves  its  problems 
as  it  meets  them  in  the  actual  physical  performance  of  man- 
ufacturing, while  the  machinery  is  running — engineering 
solves  just  as  many  problems  as  it  can  mentally  visualize 
and  work  out  on  paper  before  any  wheels  are  turned. 

The  Inspection  Department 

It  would  seem  that  the  next  logical  step  in  this  process 
of  analysis  must  reveal  inspection,  which  has  the  duty  of 
passing  upon  the  results  of  production  after  the  latter  has 
endeavored  to  carry  out  the  plans  of  engineering.  Inspec- 
tion work  is  retrospective.  It  is  performed  after  work  has 
been  done. 

Each  of  these  three  main  groups  of  functions  calls  for 
special  experience  and  for  its  own  characteristic  and  pecul- 
iar attitude  of  mind.  Engineering  and  inspection  are  the 
primary  contributories  of  production,  while  all  other  fac- 
tory activities  are  secondary  in  the  sense  of  being  merely 
general  service  duties. 

A  Parallel  with  Governmental  Organization 

It  is  not  difficult  to  find  a  parallel  case  in  a  field  of  admin- 
istration much  older  and  wider  than  the  industrial  organiza- 
tion. The  experience  of  men  in  evolving  governments  for 
social  administration  has  developed  the  necessity  for 
three  main  functions,  which  assure  stability  through  mutual 


68  THE  CONTROL  OF  QUALITY 

independence  of  authority  in  action,  but  with  interdepend- 
ence and  mutual  helpfulness  through  balancing  each  other, 
just  as  there  must  be  three  points  of  support  for  stable 
equilibrium.  The  three  governmental  functions  referred  to 
are,  of  course,  the  legislative,  executive,  and  judicial.  It  is 
easy  to  trace  their  correspondence  with  engineering,  pro- 
duction, and  inspection,  respectively,  which  have  the  same 
general  relationships.  Inspection  is  judicial  because  it  is 
measurement  plus  judgment.  If  it  were  easy  to  distinguish 
between  the  right  and  the  wrong  execution  of  either  laws  or 
plans,  there  would  be  little  need  of  applying  independent 
judgment,  but  in  very  many  cases  it  is  not  easy.  In  the  one 
as  in  the  other,  in  the  factory  as  in  civil  procedure,  the  best 
results  demand  for  their  attainment  that  the  final  applica- 
tion of  judgment  be  made  with  authority  subordinate  only 
to  the  supreme  controller  of  all  three  functions. 

Inspection's  Relation  to  Engineering  and  Production 

If  there  is  any  one  thing  that  the  management  of  a  large 
industrial  enterprise  needs  in  its  business,  it  is  the  unvar- 
nished truth  about  what  is  really  going  on  in  the  plant — not 
the  reports  from  an  espionage  system,  but  the  plain  facts 
brought  frankly  into  the  open  as  to  where  errors  are  most  fre- 
quently made,  the  extent  to  which  they  occur,  and  the  causes 
of  production  choke-points.  It  is  just  as  useful  to  know  in 
detail  what  has  been  done  as  the  work  proceeds,  as  it  is  to 
know  what  you  are  going  to  try  to  do  before  you  begin.  If 
an  engineer-executive  has  the  facts  he  usually  can  cure  the 
trouble.  Yet  ordinarily  this  information  is  the  hardest  to 
obtain,  either  promptly  or  accurately.  The  chance  of  get- 
ting it  is  much  better,  and  under  good  management  it  is 
assured,  if  there  is  competent  personnel  in  an  unbiased 
position  to  observe,  locate,  and  report  the  difficulties  as  they 
appear.  This  is  a  duty  that  the  inspection  department  is 


INSPECTION  DEPARTMENT  IN  ORGANIZATION  69 

best  able  to  perform  by  reason  of  its  freedom  from  respon- 
sibility for  anything  except  passing  upon  quality.  Here  is 
another  reason  why  the  inspection  department  should  be 
subordinate  only  to  the  management.  There  is  a  great 
value  in  having  inspection  in  what  might  be  termed,  to  fol- 
low the  above  analogy,  a  judicial  position ;  but  that  value  is 
seriously  abridged  if  inspection  is  subordinate  to  either  the 
engineering  department  or  the  production  department. 

Failure  to  obtain  both  the  standard  of  quality  and  the 
scheduled  output  will  occur  from  faulty  engineering  or  from 
a  failure  of  the  production  department  to  carry  out  properly 
the  engineering  plans.  If  inspection  is  subordinate  to  en- 
gineering, the  faults  of  engineering  will  not  come  to  light 
when  they  should.  That  is  only  human — but  it  is  not 
scientific.  Worse  still,  if  inspection  is  subordinate  to  pro- 
duction, not  only  the  latter's  faults  will  be  concealed  but 
also  there  will  be  a  strong  tendency  to  skimp  quality. 
When  once  quality  is  allowed  to  slip,  costly  losses  will  soon 
result  in  fact,  although  frequently  not  detected. 

Purpose  Help — Not  Mere  Criticism 

When,  however,  inspection  is  raised  to  its  proper  posi- 
tion and  is  assigned  the  important  duty  of  bringing  the 
facts  to  the  surface,  it  should  be  clearly  shown  to  the  other 
departments  that  the  purpose  is  one  of  mutual  helpfulness 
and  service,  and  not  one  of  destructive  criticism.  Facts 
are  necessary  to  solve  problems.  If  they  are  presented  in  a 
spirit  of  helping  to  conquer  difficulties,  surely  no  one  can 
take  offense. 

Quality  is  a  variable.  Everyone  makes  mistakes.  It  is 
immaterial  who  is  to  blame  for  them.  It  is  folly  to  be  forever 
in  search  of  a  "goat"  when  things  go  wrong;  the  precious 
time  thus  spent  should  be  used  more  constructively.  It  is 
essential  merely  that  the  mistakes  be  promptly  located, 


70  THE  CONTROL  OF  QUALITY 

recognized,  and  cured  before  loss  piles  up.  The  group  of 
workers  in  the  best  position  to  do  this  are  those  in  the  least 
prejudiced  situation  and  hence  best  able  to  see  things  as 
they  really  are.  There  can  be  but  one  conclusion,  namely 
that  the  inspection  department  should  perform  this  service. 
But  it  cannot  do  that  efficiently  if  its  hands  are  tied. 

The  Real  versus  the  Apparent  Organization 

In  the  majority  of  factories,  especially  before  the  war, 
factory  inspection  received  little  recognition.  Even  now, 
in  very  few  factories  indeed  is  it  given  a  chance  to  demon- 
strate its  greatest  possibilities  for  service.  In  nearly  all 
plants,  however,  even  those  which  are  comparatively  small, 
the  latent  possibilities  of  inspection  can  be  developed  if  the 
real  organization  is  made  more  nearly  like  the  apparent 
organization.  The  difference  between  the  two  is  often 
considerable. 

What  maybe  termed  the  "apparent"  organization  is  that 
shown  by  the  assignment  of  duties  in  the  form  of  an  organi- 
zation chart,  or  perhaps  by  the  titles  given  to  the  various 
department  heads  and  their  assistants.  Often,  however, 
the  actual  work  is  not  carried  out  in  accordance  with  the 
apparent  organization.  Certain  individuals  will  be  found 
to  be  exerting  a  far  greater  influence  than  their  assigned 
positions  would  seem  to  indicate.  If  the  organization 
chart  were  redrawn  to  show  the  true  way  in  which  duties  are 
carried  out  rather  than  how  they  are  assigned  in  theory,  and 
to  indicate  clearly  a  relationship  between  individuals  in 
accordance  with  their  proportionate  contribution  to  the 
enterprise,  then  it  would  indicate  the  real  organization. 

If  an  organization  is  analyzed  with  this  test  in  mind,  the 
discovery  will  probably  be  made  that  the  inspection  depart- 
ment's contribution  is  greater  than  the  apparent  organiza- 
tion would  seem  to  indicate.  If  it  is  exalted  to  a  position 


INSPECTION  DEPARTMENT  IN  ORGANIZATION 


72  THE  CONTROL  OF  QUALITY 

equal  to  that  of  production  and  engineering,  it  will  give 
a  still  greater  return.  If  it  is  subordinated,  its  greatest 
potentialities  will  be  lost. 

Engineering  and  Inspection 

As  has  been  stated  elsewhere,  the  working  or  practical 
standards  of  quality  are  furnished  in  the  main  by  the  en- 
gineering department.  These  standards  serve  well  enough 
for  work  that  is  plainly  seen  to  be  well  inside  the  limits  or 
well  outside  the  limits.  The  difficulty  in  fixing  standards  of 
quality  accurately  arises  from  the  large  proportion  of  work 
which  falls  close  to  the  limits. 

At  this  point  the  engineering  department  must  be  re- 
leased in  favor  of  the  inspection  department,  for  in  such 
cases,  in  the  last  analysis,  someone  must  make  up  his  mind 
as  to  whether  the  work  should  be  passed  or  rejected.  Thus 
the  element  of  personal  judgment  enters,  and  a  specialized 
technique  must  be  cultivated  and  applied.  For  judgment 
varies  as  between  individuals,  and  in  the  same  individual  at 
different  times.  To  this  fact  may  be  ascribed  many  of  the 
phenomena  of  the  inspection  of  close  work,  where  only  a 
small  percentage  of  parts  are  made  that  cannot  be  rejected 
on  some  technicality.  This  is  the  case  with  respect  to  di- 
mension, and  still  more  with  respect  to  matters  of  finish, 
because  judgment  is  accentuated  so  much  more  in  inspect- 
ing for  finish.  Now  the  value  of  judgment  depends  upon 
its  freedom  from  influence. 

Production  and  Inspection 

The  inspection  department's  relation  to  the  whole  or- 
ganization is  judicial  rather  than  creative.  It  is  responsible 
to  the  management  for  detecting  failures  in  quality,  and  in 
that  sense  it  bears  a  very  heavy  responsibility  for  the  main- 
tenance of  standards.  It  does  not  manufacture,  however, 


INSPECTION   DEPARTMENT  IN  ORGANIZATION  73 

and  therefore  when  poor  work  is  produced  the  production 
department  cannot  usually  shift  the  blame  to  the  inspection 
department.  The  production  department  should  be  made 
to  realize  that  it  is  itself  responsible  for  the  quality  of  its 
product — it  makes  the  work  right  or  it  makes  it  wrong.  If 
the  production  force  is  organized  by  operations,  the  in- 
dividual subforeman,  tool-setter,  or  adjuster  in  charge  of 
each  operation  should  be  made  to  feel  that  he  is  responsible 
for  the  quality  of  the  work  produced  under  his  direction. 
In  addition  to  checking  the  work  frequently  in  person,  he 
may  be  required  to  bring  the  first  two  or  three  pieces  made 
after  each  new  machine  set-up  to  the  inspector  for  verifying, 
but  merely  as  a  guide  in  his  own  work.  Both  departments 
then  bear  a  definite  responsibility  to  the  management  for 
quality,  but  independently  and  in  different  ways. 

It  is  a  well-accepted  principle  that  responsibility  should 
be  re-enforced  by  adequate  authority.  Accordingly,  if  in- 
spection is  charged  with  the  responsibility  of  stopping  losses 
from  work  not  up  to  standard,  it  must  be  given  the  authority 
to  stop  machines.  When  this  authority  is  granted,  it  is 
only  good  judgment  to  specify  an  exact  procedure  for  advis- 
ing the  responsible  production  executive,  also  for  putting 
the  machine  back  into  production.  It  hardly  need  be  added 
that  such  authority  is  not  likely  to  be  used  if  the  inspection 
department's  freedom  is  restricted  by  its  subordination  to 
production. 

In  fact,  if  inspection  is  to  develop  its  greatest  possibilities 
for  service,  it  requires  room  to  work  and  a  free,  fair  chance 
to  solve  its  problems.  If  you  believe  in  inspection  suffi- 
ciently to  have  an  inspection  department,  why  not  give  it 
a  chance  to  show  what  it  can  do  ? 


CHAPTER  VI 

INSPECTION'S  CONTRIBUTION  TO  GENERAL 
SERVICE 

The  Collection  of  Useful  Information 

One  of  the  greatest  benefits  of  the  inspection  service 
comes  from  its  power  to  bring  promptly  to  the  attention  of 
the  management  information  as  to  the  true  state  of  affairs 
in  the  shops.  No  tool  is  so  useful  to  the  manager  as  knowl- 
edge of  the  facts,  yet  nothing  is  so  hard  to  obtain.  The 
foreman-inspector  of  each  shop  is  very  close  to  what  is  going 
on  in  that  shop,  and  is  likely  to  be  in  the  most  unbiased 
state  of  mind  because  he  is  an  observer  rather  than  a 
producer. 

Counting  the  work  done  and  certifying  to  it  is  part  of 
the  inspector's  duty  as  a  matter  of  course.  Summarizing 
this  information  for  reports  to  be  used  for  the  purposes  of 
the  pay-roll,  the  cost  records,  and  the  production  records 
may  or  may  not  be  a  part  of  his  duty,  depending  on  the 
character  of  the  work.  If  this  warrants  a  well-developed 
inspection  system,  it  is  quite  likely  that  the  foreman-in- 
spector of  every  sizable  department  will  require  clerical 
assistance.  If  so,  this  clerk  may  just  as  well  assemble  the 
count  of  work  performed  in  his  department,  before  it  is 
transmitted  to  the  general  factory  offices.  When  produc- 
tion and  cost  data  are  assembled  and  analyzed  by  the  use  of 
power-driven  tabulating  machines,  the  data  may  be 
collected  at  the  original  sources  and  its  accuracy  certified 
to  by  the  inspectors,  with  the  obvious  advantage  of  securing 
competent  assistance  in  gathering  the  information  together 
with  the  resultant  saving  in  clerical  expense.  The  addi- 

74 


INSPECTION'S  CONTRIBUTION  TO  SERVICE  75 

tional  burden  on  the  inspector  is  slight,  and  the  added  duty 
may  even  be  beneficial  because  it  tends  to  bring  him  closer 
to  his  job. 

There  is  another  sort  of  information  of  equal  or  of  even 
greater  importance,  which  the  inspector  evidently  is  in  the 
best  position  to  obtain ;  namely,  the  location  of  production 
troubles,  the  isolation  of  their  causes,  and  frequently  the 
offering  of  suggestions  for  their  cure.  Production  difficulties 
ordinarily  appear  in  the  form  of  too  great  losses  in  spoilage, 
or  through  the  slowing  down  of  production  at  some  opera- 
tion, thus  creating  a  choke-point  or  a  partial  choke-point. 
It  is  essential,  of  course,  to  correct  the  difficulty  as  soon  as 
possible,  but  to  do  this  it  is  necessary  to  develop  and  bring 
to  light  the  true  causes. 

Trouble  Reports 

A  very  useful  device  for  the  prompt  collection  of  such 
data  may  be  secured  by  providing  a  printed  form  of 
" trouble  report"  to  be  made  out  and  sent  by  foremen- 
inspectors  of  shops  to  the  chief  inspector,  who  will  transmit 
such  facts  as  seem  worth  attention  to  the  department  that 
should  correct  the  trouble — the  management  being  fur- 
nished with  a  copy.  The  trouble  report  should  read  pref- 
erably as  shown  in  Figure  13. 

A  detailed  list  of  usual  soruces  of  trouble,  such  as  tools, 
gages,  material,  and  so  on,  may  be  added  for  convenience, 
but  the  essential  idea  is  to  make  the  foreman-inspector  feel 
the  responsibility  for  promptly  reporting  the  facts  and 
nothing  but  the  facts.  Hence  the  requirement  that  he 
must  state  either  that  he  "knows"  or  that  he  merely 
"thinks"  that  the  trouble  is  due  to  the  cause  stated  in  his 
report.  For  the  trouble  report  to  be  used  successfully,  the 
foreman-inspector  must  have  confidence  in  the  judgment, 
fairness,  and  courage  of  his  chief — he  must  feel  sure  that  he 


76  THE  CONTROL  OF  QUALITY 


From Foreman- Inspector 

To  Chief  Inspector 

Shop Date 

Operation Hour 

I  report  the  following  trouble 

I  know  think  (scratch  out  one)  that  the  trouble  is  due  to  the  following 


Figure  13.     Trouble  Report 

will  be  backed  up  if  he  is  right.  Further,  the  management 
should  make  quite  clear  that  it  is  looking  for  facts  in  order 
to  cure  troubles,  and  not  to  find  someone  to  blame.  There 
is  no  surer  way  to  put  a  premium  on  the  concealment  of 
facts  than  by  trying  to  fix  the  blame  on  an  individual,  nor 
does  blaming  someone  help  to  cure  the  trouble.  Presum- 
ably each  executive  holds  his  job  because  he  is  the  best 
available  man  for  the  position.  If  he  is  not,  the  manage- 
ment will  know  it  much  sooner  if  he  and  his  associates  are 
not  continually  placed  in  the  position  of  being  called  upon 
to  make  excuses. 

The  Inspector's  Sense  of  Responsibility 

Certain  phases  of  the  psychology  involved  in  trouble 
reports  deserve  more  detailed  consideration  at  this  point. 
In  the  first  place,  if  the  device  of  the  trouble  report  is  to  be 
successfully  applied  the  inspector  must  be  made  to  feel  that 


INSPECTION'S  CONTRIBUTION  TO  SERVICE  77 

he  is  exercising  a  trust,  and  that  the  management  reposes 
unusual  confidence  in  his  impartiality  and  adherence  to 
accuracy.  This  feeling  on  his  part  has  two  very  practical 
results:  first,  the  information  will  be  more  truthful;  second, 
the  inspector  will  perform  his  other  duties  with  the  increased 
efficiency  that  flows  from  a  stronger  realization  of  his  value 
to  the  organization.  There  are  very  few  men  who  will 
not  rise,  in  spirit  as  well  as  in  act,  to  meet  increased 
responsibilities. 

At  the  same  time  the  inspector  should  be  made  to  know 
positively  that  accuracy  will  be  insisted  on.  The  latter 
purpose  is  accomplished  by  requiring  him  to  state  in  each 
report  whether  he  knows  what  he  is  talking  about,  or  merely 
thinks  the  situation  is  thus  and  so.  Quite  a  distinction  is 
involved,  of  course,  both  in  the  report  itself,  as  well  as  in  the 
action  likely  to  be  taken.  On  the  other  hand,  provided  the 
inspector  truthfully  states  the  degree  of  his  belief  as  to  the 
facts,  it  is  of  comparatively  little  importance  which  form 
the  report  takes. 

A  Typical  Instance 

Experience  with  the  trouble  report  as  used  in  a  very 
large  and  highly  organized  inspection  department  developed 
some  very  interesting  reactions.  This  form  of  report  was 
designed  to  meet  a  special  set  of  conditions,  first,  because  it 
was  vitally  important  to  get  the  best  available  information 
about  a  complex  manufacturing  situation  as  soon  as  pos- 
sible; and  second,  because  stiffening  up  the  morale  was 
judged  to  be  the  most  important  thing  in  reorganizing  this 
particular  inspection  department.  A  few  days  after  the 
form  of  report  was  placed  in  the  hands  of  the  foremen- 
inspectors,  reports  began  to  come  in  without  either  verb 
"know"  or  " think"  scratched  out.  That  was  to  be  ex- 
pected, as  the  inspection  force  had  been  led  to  feel  that  its 


78  THE  CONTROL  OF  QUALITY 

work  might  be  performed  negligently  or  otherwise  without 
visible  effect  on  the  running  of  the  plant.  All  such  indefi- 
nite reports,  however,  were  returned  promptly  with  the  re- 
quest that  they  be  corrected  in  this  respect.  The  inference 
was  clear  that  the  reports  were  considered  of  value  and  were 
to  be  used.  Some  of  those  which  had  been  returned  never 
came  back,  as  was  hoped,  and  the  total  number  of  reports 
became  less.  But  over  QO  per  cent  of  those  which  did  come 
in  read  "I  know."  This  is  the  thing  to  note  especially. 
When  the  management  began  to  take  action  on  the  more 
important  reports,  the  inspectors'  growing  feeling  of  re- 
sponsibility was  confirmed  by  seeing  things  begin  to  happen, 
and  the  effect  on  the  morale  of  the  entire  department  was 
very  marked. 

Reception  of  Trouble  Reports 

As  stated  at  first,  the  use  of  such  reports  carries  with  it 
the  necessity  of  using  them  in  the  spirit  in  which  all  scien- 
tifically trained  minds  should  work.  They  should  be 
received  as  being  presented  in  a  spirit  of  helpful  and  con- 
structive criticism  and  as  the  opinion  of  an  impartial  ob- 
server reporting  things  as  he  views  them.  The  department 
whose  work  is  most  involved  must  be  made  to  feel  that  this 
is  the  way  the  report  is  offered,  and  to  accept  it  in  the  same 
spirit.  If  the  report  is  not  well  founded,  no  one  is  reflected 
upon  so  much  as  the  inspector.  If  the  report  is  correct  no 
one  should  be  so  glad  to  discover,  and  to  correct  the  trouble 
as  the  department  responsible  for  the  trouble.  To  secure 
this  co-ordination  and,  in  fact,  to  require  a  spirit  of  mutual 
confidence  and  good-fellowship,  is  distinctly  the  duty  of  the 
management.  This  is  apparently  a  small  point,  but  it  is 
vital. 

The  use  of  some  such  report  will  yield  just  as  valuable 
returns  in  many  other  kinds  of  work  than  factory  inspection 


INSPECTION'S  CONTRIBUTION  TO  SERVICE  79 

in  its  more  limited  sense.     Figure  14  is  an  example  of  a 
form  adapted  to  use  in  a  great  ship  assembling  plant.1 

Inspection  and  the  Assembling  Department 

After  the  various  component  parts  have  passed  inspec- 
tion in  the  respective  parts-making  shops  and  have  been 
placed  in  the  finished-parts  stores  prior  to  being  issued  to 
the  assembling  department,  it  may  be  assumed  with  reason- 
able assurance  that  they  can  be  assembled  satisfactorily. 
There  is  an  ever-present  tendency,  however,  for  work  to  slip 
away  from  the  desired  standards  of  quality,  and  to  do  so  by 
such  small  daily  increments  that  the  changes  are  difficult  of 
detection.  Measuring  devices,  whether  gages  or  precision 
instruments  of  more  general  type,  and  cutting  tools,  are 
subject  to  wear  like  everything  else.  The  fact  that  the 
wear  does  not  take  place  rapidly  or  evenly  makes  the 
process  all  the  more  subtle  and  insidious.  Then  there  is  al- 
ways the  chance  of  a  gage  being  accidentally  injured,  and 
work  incorrectly  disposed  of,  in  consequence.  In  close 
work,  as  already  noted,  these  troubles  are  accentuated  by 
personal  errors  and  by  a  multitude  of  other  influences. 

The  net  effect  is,  that  in  spite  of  every  reasonable  precau- 
tion quality  will  slip,  and  the  errors  may  not  be  detected 
until  the  parts  are  issued  for  assembling.  If  the  errors  are 
due  to  gradual  wear  or  similar  cause,  the  condition  will  be 
manifested  first  by  a  slowly  increasing  difficulty  in  assem- 
bling, which  is  more  dangerous  than  an  absolute  failure  to 
assemble.  For  example,  a  part  may  assemble  satisfactorily, 
and  even  pass  final  tests  in  the  assembled  mechanism,  and 
still  be  just  enough  outside  the  lowest  permissible  limits  to 
wear  into  a  non-functioning  shape  after  a  short  time  in  ac- 
tual service. 


1  Furnished  through  the  courtesy  of  William  B.  Ferguson,  formerly  Assistant  to  the  President 
and  Manager  of  the  Division  of  Standards,  American  International  Shipbuilding  Corporation 
(Hog  Island). 


80  THE  CONTROL  OF  QUALITY 


FROM  WAY  No . 


AGREEMENT  No. PIECE  MARK DRAWING  No. 

AGREEMENT  NAME .... . 


LOCATION  OF  WORK. 


1  FAULTY  MATERIAL?  FAULTY  WORKMANSHIP? 

2  HAD  WORK  BEEN  COMPLETED  ON  WAYS 


3  COULD  FAULT  HAVE  BEEN  CAUGHT  BY  MORE  CAREFUL  INSPECTION*! 

4  IN  YOUR  OPINION  SHOULD  WORK  HAVE  BEEN  PASSED  ON  WAYS? 

5  To  WHOM  SHOULD  THIS  BE  REPORTED  SO  THAT  IT  WILL  NOT 
OCCUR  AGAIN' 


JOB  STARTED JOB  FINISHED, 


No.  OF  MEN  ON  JOB No.  OF  MAN  HOURS, 

DESCRIPTION  OF  FAULT 


SIGNED 


Figure    14.     Inspection    Form — American    International    Corporation,    Hog 

Island 


INSPECTION'S  CONTRIBUTION  TO  SERVICE  8l 

There  was  a  particular  make  of  engine  of  excellent  and 
even  very  advanced  design,  which  nevertheless  failed  in 
certain  cases,  most  unexpectedly,  after  being  used  for  a 
short  time.  A  cursory  viewing  of  the  factory's  inadequately 
controlled  inspection  system  revealed  an  obvious  reason  for 
the  service  troubles  which  were  killing  future  business. 
Parts  of  the  mechanism  of  the  engine  in  question  required 
very  accurate  work.  Some  of  these  parts,  with  proper  in- 
spection lacking,  were  found  to  be  just  good  enough  to  pass 
factory  tests,  but  not  good  enough  to  stand  up  long  in  ac- 
tual use. 

Benefits  to  Entire  Factory 

With  a  highly  organized  inspection  service  in  the  shops 
and  extending  into  the  subassembly  and  final  assembly 
rooms,  a  means  is  provided  for  avoiding  such  difficulties. 
The  direct  work  of  inspecting  in  the  assembling  department 
is  often  of  less  value,  however,  than  the  collection  of  infor- 
mation of  value  to  the  rest  of  the  factory.  The  assembling 
rooms  are  a  particularly  fertile  field  for  revealing  errors,  and 
the  inspection  department,  for  the  reasons  previously  stated, 
is  specially  in  a  position  to  catch  these  errors  and  to  pass  the 
word  about  them  back  into  the  factory  for  the  help  and 
guidance  of  all.  Time  is  a  vital  factor  in  such  matters,  and 
a  well-organized  inspection  service  will  be  able  to  send  the 
warning  back  along  the  line  with  the  proper  speed.  The 
possibilities  of  such  a  service  are  so  great  that  it  may  be  the 
part  of  wisdom  to  place  the  assembling  under  the  general 
control  of  the  head  of  the  inspection  department,  especially 
if  such  a  combination  of  duties  will  serve  as  a  further  reason 
for  selecting  a  man  of  larger  caliber  for  that  important 
position. 

Curiously  enough,  if  the  work  is  not  strictly  inter- 
changeable there  is  often  a  greater  reason  for  increasing  the 


82  THE  CONTROL  OF  QUALITY 

importance  of  the  inspector's  position  in  the  assembling 
department.  In  this  case,  of  course,  selection  of  parts  be- 
comes necessary.  Very  often  it  can  and  should  be  made  a 
separate  operation  from  that  of  putting  the  parts  together. 
The  work  of  choosing  parts  that  will  mate  properly  in- 
volves measuring  the  parts  and  then  sorting  them  out  in  a 
systematic  manner  into  a  few  groups,  each  of  which  is  made 
up  of  parts  of  very  nearly  the  same  dimension.  The  proc- 
ess is  simpler  if  the  work  is  of  a  character  to  warrant  the 
use  of  selective  gaging.  It  is  merely  an  extension  of  division 
of  labor  to  separate  this  work  of  sorting  from  that  of  as- 
sembling, and  the  sorting  is  more  closely  allied  to  inspection 
than  it  is  to  production. 

An  Example  of  Selective  Assembly 

An  example  of  this  kind  is  to  be  found  in  the  manufac- 
ture of  rifles  or  pistols  which  have  raised  sight-bases  integral 
with  the  barrel.  The  barrel  has  a  milled  thread  which 
screws  into  a  similarly  threaded  opening  in  the  receiver  or 
frame.  The  barrel  must  screw  into  the  frame  so  that  the 
sight-bases  are  in  line  with  the  vertical  plane  of  the  frame 
(to  insure  correct  alignment  of  the  sights) ;  and,  in  addition, 
the  barrel  and  receiver  must  be  drawn  together  at  a  given 
tension,  this  "draw"  being  required  to  be  between  given 
limits  expressed  in  pounds  for  a  stated  lever  arm  or  length  of 
wrench.  Both  barrel  and  frame  require  many  operations 
before  they  are  ready  for  assembling,  and  several  of  these 
operations  are  referred  back  to  the  location  of  the  milled 
threads  and  sight-bases.  Needless  to  say,  it  is  not  always 
the  simplest  matter  in  the  world  so  to  locate  and  mill  the 
threads  as  to  fulfil  the  two  conditions  of  sight  alignment  and 
draw  of  threaded  joint,  while  still  conforming  to  full  inter- 
changeability.  Therefore,  if  a  proportion  of  the  parts  de- 
mand selective  assembling,  a  very  considerable  amount  of 


INSPECTION'S  CONTRIBUTION  TO  SERVICE  83 

work  can  be  saved  if  the  parts  are  separately  gaged,  with 
gages  provided  with,  say,  10  numbered  stages,  to  indicate 
corresponding  positions  in  relation  to  the  draw  marks  when 
the  gages  are  set  up  with  a  fixed  turning  moment  of,  say, 
n  pounds  at  the  end  of  a  wrench  a  inches  long.  The  female 
gage  applied  to  the  barrel  and  the  male  gage  applied  to  the 
frame  are  so  calibrated  that  barrels  drawing  to  point  8  on 
the  barrel-gage,  for  example,  will  properly  mate  with  frames 
drawing  to  point  8  on  the  frame-gage,  and  so  on;  and  the 
parts  will  be  sorted  accordingly  before  issuing  to  the  as- 
semblers. 

This  method  may  be  applied  in  principle  to  many  cases 
in  which  economy  in  making  the  parts  indicates  the  desir- 
ability of  selective  assembly.  It  will  be  noted  that  what 
really  happens  is  that  by  means  of  the  inspection  and  sorting 
of  parts  the  assembling  advantages  of  true  interchangeabil- 
ity  are  secured. 

The  Custody  of  Work  in  Process 

Many  factories  possessing  very  complete  systems  for 
production  control  are  more  concerned  with  the  paper 
records  of  the  system  than  they  are  with  the  systematic  and 
orderly  arrangement  of  the  work  in  process  of  manufacture 
in  the  shops.  The  machinery  may  very  likely  be  arranged 
to  secure  the  best  possible  compromise  for  straight-line 
routing.  If  the  work  is  large  in  volume  and  concentrated  on 
one  product,  the  machines  are  arranged  in  the  order  of  the 
operations,  so  that  work  flows  from  machine  to  machine  in 
regular  sequence.  If  the  work  is  varied  in  character,  the 
machines  are  arranged  by  classes,  as  lathes,  planers,  millers, 
and  so  forth.  In  either  case  it  is  likely  that  planning  and 
routing  are  well  cared  for  in  any  modern  shop.  It  is  a 
common  fault,  however,  for  the  work  in  process  to  be  piled 
all  over  the  shop.  Even  if  the  work  flows  directly  from 


84  THE  CONTROL  OF  QUALITY 

machine  to  machine,  it  is  no  unusual  sight  to  observe  parts 
rusting  at  the  bottom  of  a  pile  where  they  have  lain  for 
months,  or  other  parts  in  like  condition  under  an  inspector's 
bench. 

The  first  point  to  be  determined  is  whether  this  condition 
should  be  corrected.  In  certain  instances,  as  in  a  great 
shipyard  machine  shop,  the  change  may  not  be  practicable. 
In  most  cases,  however,  it  is  worth  while  to  make  the  effort ; 
nor  need  it  involve  much  expense,  provided  there  is  an 
effectively  organized  and  managed  inspection  department  to 
which  this  duty  can  be  turned  over.  If  central  inspection  is 
in  use  the  job  is  readily  taken  care  of.  If  not,  the  inspector 
at  least  can  guide  the  work  into  a  more  orderly  arrangement 
if  he  is  given  the  authority  to  have  work  moved  to  the  next 
machine  after  he  has  passed  it.  The  placing  of  work 
naturally  carries  with  it  the  custody  of  work  in  process.  A 
little  encouragement  of  the  inspection  department  will 
develop  a  "fatherly"  interest  in  the  work  itself,  from  which 
will  flow  a  more  orderly  shop. 

Stimulus  to  Order  and  Cleanliness 

While  considering  the  advantages  obtained  by  a  more 
systematic  arrangement  of  the  shop  as  regards  work  in  proc- 
ess, the  effect  of  order  (and  the  greater  shop  cleanliness  it 
permits)  upon  the  working  force  should  not  be  overlooked. 
An  artist's  temperament  may  be  suited,  perhaps,  to  doing 
good  work  under  messy  conditions,  but  the  average  man 
does  better  work  if  his  environment  is  orderly  and  clean. 
It  is  well  recognized  that  a  desk  covered  with  papers  is  not 
desirable.  It  has  come  to  be  regarded  as  an  indication  of  a 
mind  in  the  same  condition  as  the  desk.  Does  not  the  same 
criterion  hold  in  the  shop? 

The  first  step  in  securing  order,  if  a  reasonably  good  shop 
arrangement  exists,  is  the  prompt  sorting  out  of  work  as  it 


INSPECTION'S  CONTRIBUTION  TO  SERVICE  85 

leaves  the  machine,  followed,  of  course,  by  a  systematic 
placing  of  the  work  after  it  has  been  sorted. 

The  Analysis  of  Work  in  Process— "Good"  and  "Bad" 

Sorting  out  work  in  process  by  inspection  requires  the 
guidance  of  some  sort  of  classification;  the  matter  cannot  be 
dismissed  by  merely  saying  that  work  is  good  or  bad.  The 
parts  or  pieces  of  work  that  are  passed  by  the  inspector  may 
be  designated  as  "good  parts"  or  "good  work,"  as  this  ter- 
minology is  brief,  and  the  term  "good  work"  is  definite  and 
accurate  enough,  provided  we  remember  that  the  work  is 
probably  up  to  standard.  As  there  is,  of  course,  the  men- 
tal reservation  that  the  inspector  may  be  wrong,  there  is  a 
necessity  for  applying  sampling  tests  to  good  parts  from 
time  to  time,  and  for  surrounding  the  inspector's  work  with 
safeguards,  as  set  forth  in  Chapter  IV.  Parts  obviously 
good  require  no  other  treatment  than  to  be  passed  on  to 
the  next  stage  in  their  manufacture,  assuming  that  some 
definite  place  is  assigned  for  their  temporary  storage  until 
the  succeeding  operation. 

"Rejected  work,"  that  is  to  say,  "bad  work,"  calls  for 
analysis  into  several  classes  with  appropriate  definitions  for 
each  class.  As  in  the  case  of  good  work,  allowance  must 
be  made  for  the  possibility  of  error  on  the  inspector's  part. 
Provision  should  be  made  so  that  work  rejected  on  the  first 
inspection  may  have  some  chance  of  reinspection.  It  is 
quite  the  usual  thing  in  the  inspection  of  all  kinds  of  work, 
from  shipbuilding  to  small  interchangeable  and  high-grade 
parts,  to  have  some  of  the  rejected  work  really  fit  for  passing. 

Handling  Rejected  Parts 

Next  comes  up  the  question  of  how  the  rejects  should  be 
handled — we  are  concerned  principally  with  interchangeable 
parts  because  such  work  furnishes  the  widest  range  of  ex- 


86  THE  CONTROL  OF  QUALITY 

amples  illustrative  of  inspection.  The  first  step  is  to  sort 
out  those  which  require  only  a  remachining  on  the  machine 
from  which  they  just  came.  Usually  too  little  metal  has 
been  removed,  or  further  polishing  is  required,  and  the 
work  can  be  made  good  by  the  shop  itself.  Ordinarily  this 
work  should  be  done  by  the  machine  operator  who  did  the 
work  in  the  first  place,  and  on  his  own  time.  Of  like  nature 
are  the  instances  of  parts  with  certain  operations  missing; 
also  those  which  are  best  repaired  on  jigs  and  fixtures  avail- 
able only  in  the  shops. 

The  rejects  remaining  after  taking  out  the '  'shop  repairs" 
should  be  accumulated  at  some  point  in  the  shop,  preferably 
in  a  space  set  aside  as  the  shop  salvage  space  and  under  the 
care  of  the  inspection  department.  At  this  stage,  when 
sufficient  rejects  are  accumulated  to  warrant  the  work,  a 
reinspection  should  be  made,  in  which  the  parts  are  sepa- 
rated into  two,  or  possibly  three  classes,  as  follows: 

I.  Spoiled  parts,  which  should  be  sent  to  the  factory 
salvage  room  to  be  kept  under  lock  and  key;  for  if  this  is  not 
done,  some  of  them,  under  stress  for  production,  are  apt  to 
find  their  way  back  into  process  by  some  path  or  other.  In 
the  salvage  department  they  will  be  carefully  examined 
with  a  view  to  their  conversion  into  the  most  marketable 
form,  either  as  scrap  or  otherwise.  Circumstances  will  indi- 
cate whether  they  should  be  mutilated  to  prevent  their  use 
except  as  scrap,  or  sold  as  they  are  for  use  in  another  article. 
Springs,  for  example,  rejected  as  below  your  own  standard  of 
quality,  may  be  sold  to  a  consumer  whose  needs  are  less 
exacting.  You  can  afford  to  supply  him  at  a  lower  price 
than  he  would  otherwise  pay,  and  both  of  you  make  money. 
A  cleverly  handled  salvage  department,  which  classifies  the 
scrap  from  a  large  factory  in  this  way,  and  which  is  alertly 
in  search  of  better  markets  for  its  goods,  is  a  money-maker 
in  itself. 


INSPECTION'S  CONTRIBUTION  TO  SERVICE  87 

2.  Rejected  parts  which  require  special  work  to  bring 
them  up  to  standard  but  which  exist  in  sufficient  quantity  to 
warrant  such  repairs  should  be  sent  to  a  separate  parts-re- 
pairing department  or  ''hospital, "  specially  designated  as 
such,  and  located  clear  of  the  regular  production  depart- 
ments. This  is  the  place  for  the  all-round  mechanic  with  a 
taste  for  improvising  and  inventing.  Supply  this  little  shop 
with  a  few  general  utility  machines,  welding  outfits,  and  so 
on,  and  considerable  loss  will  be  avoided.  Apply  the  most 
rigorous  inspection  both  to  its  work  during  the  repairs  and 
to  its  output. 

In  the  course  of  repairing  some  parts,  occasions  may 
arise  when  it  is  necessary  for  the  repair  department  to  send 
the  work  out  into  the  factory  for  some  treatment  or  process 
beyond  the  repair  shop  capacity.  If  this  occurs,  by  all 
means  provide  a  special  routing  card  of  distinguishing  color 
to  go  with  the  work,  and  return  the  work  to  the  repair  shop 
for  inspection.  Otherwise  the  repair  shop  inspector  can- 
not be  held  responsible  for  the  quality  of  repaired  work  of 
this  character.  In  addition,  he  knows  best  what  defects  to 
look  for  by  reason  of  his  previous  acquaintance  with  the 
parts  in  question.  Finally,  the  repair  department  should 
keep  a  follow-up  record  of  all  of  its  work  so  sent  out. 

It  is  suggested  that  very  careful  consideration  be  given 
to  the  matter  'of  a  separate  repair  shop  for  rejected  parts. 
Too  frequently  the  attempt  is  made  to  do  such  work,  or  a 
large  part  of  it,  in  the  parts-making  shops.  Then  again, 
work  is  often  scrapped  that  otherwise  would  have  been  re- 
stored to  a  perfectly  satisfactory  condition  in  a  special  repair 
shop,  whose  working  force  is  skilled  in  such  things  and  proud 
of  its  ability  to  accomplish  the  apparently  impossible. 

The  effect  on  production  of  having  repairs  made  in  the 
local  parts-making  shops  must  also  be  considered.  Such 
work  calls  for  the  more  expert  workmen,  so  that  the  repairs 


88 


THE  CONTROL  OF  QUALITY 


INSPECTION'S  CONTRIBUTION  TO  SERVICE  89 

cost  not  only  the  direct  time  of  such  men,  but  also  the  in- 
direct cost  of  lessened  output  due  to  their  separation  from 
the  regular  production  work. 

One  more  reason  for  the  separate  repair  shop:  When 
a  great  number  of  parts  are  turned  loose  in  a  large  and  com- 
plexly equipped  shop,  strange  and  curious  things  happen. 
Some  parts  are  likely  to  run  wild  unless  their  fields  of  move- 
ment are  carefully  restricted.  If  repair  work  is  superim- 
posed on  the  routine  production,  some  of  the  repairs  are 
quite  capable  of  running  in  circles.  They  are  inspected 
and  repaired,  and  inspected  again.  The  same  individual 
pieces  are  returned  for  repairs  and  then  inspected,  and  so  on 
indefinitely,  until  they  give  way  under  the  strain  of  so  much 
activity — the  best  disposition  of  them  because  really  the 
cheapest.  "Circling"  is  of  more  frequent  occurrence  than 
might  be  imagined,  because  it  is  exceedingly  difficult  to 
detect,  unless  the  work  is  of  such  a  character  that  the  in- 
spector stamps  a  mark  on  the  work  after  each  important 
inspection,  and  even  stamping  may  not  prove  effective. 
The  danger  of  circling,  however,  is  obviated  by  rigorously 
excluding  repair  work  from  the  parts-making  shops. 

3.  Under  some  conditions  it  may  be  compatible  with 
business  policy  to  consider  a  third  class  of  rejected  work. 
This  case  occurs  when  some  of  the  rejected  work  is  suitable 
for  use  in  a  second-grade  product.  Presumably  such  a 
product  will  not  be  marketed  under  the  company  label  and 
the  necessary  precautions  will  be  taken  to  insure  the  pro- 
tection of  the  reputation  of  the  company's  standard  goods, 
as  well  as  to  insure  that  the  manufacture  of  second-grade 
goods  does  not  become  the  factory's  principal  occupation. 

Quality  as  an  Incentive  to  Production 

With  work  classified  by  inspection  as  indicated  above,  it 
is  no  difficult  matter  to  count  the  work  of  each  class  and 


90  THE  CONTROL  OF  QUALITY 

tabulate  the  results.  In  this  way  the  inspection  force  pro- 
vides the  usual  production  data,  as  referred  to  in  the  preced- 
ing chapters.  The  same  information  in  somewhat  modified 
form  is  the  basic  matter  for  the  all-important  quality  records. 

Certain  of  this  information  is  of  special  interest  to  the 
individual  workman,  and  may  be  used  to  great  advantage 
in  stimulating  better  workmanship  and  thereby  greater  pro- 
duction. In  the  first  place,  the  output  of  good  parts  for  the 
day,  presented  in  simple  form,  may  be  posted  on  a  shop 
bulletin  board  devoted  to  this  purpose  only.  The  results 
should  be  contrasted  with  the  scheduled  output  desired,  and 
to  this  may  be  added  other  significant  information,  such  as 
the  statement,  for  example,  that  "Operation  No.  23  spoiled 
20  per  cent  of  its  pieces  today.  This  is  a  difficult  process, 
but  we  will  have  to  hustle  tomorrow  to  meet  the  schedule." 
Workmen  are  interested  in  this  sort  of  thing,  much  more  so 
than  might  be  supposed.  If  they  are  not,  the  fact  is  ad- 
vance notice  to  the  management  to  overhaul  the  things  that 
affect  the  good-will  of  the  so-called  " human  factor." 

Bulletin  boards,  it  may  be  said,  can  be  made  much  more 
useful  as  an  instrument  of  publicity  if  attention  is  given  to 
taking  down  notices  as  well  as  to  posting  them.  The  shop 
bulletin  board  is  too  often  plastered  with  papers  and  notices 
of  ancient  vintage.  Its  effectiveness  increases  remarkably 
if  it  is  kept  absolutely  cleared  except  when  something  is  to 
be  put  across  quickly.  Then  post  your  notice,  briefly  worded 
and  clearly  printed  in  large  type,  and  just  as  soon  as  it  has 
served  its  purpose,  have  it  taken  down,  and  the  boards  left 
clear  as  before. 

The  Individual  Worker's  Interest 

Much  of  the  data  accumulated  by  the  inspection  depart- 
ment is  of  greater  interest  to  individual  workers  than  to  the 
entire  shop  working  force,  considered  collectively.  Bill 


INSPECTION'S  CONTRIBUTION  TO  SERVICE  91 

Jones's  interest  in  his  work  can  be  stimulated  very  often  by 
showing  him  the  effect  that  his  personal  endeavors  have  had 
on  the  output  of  his  shop.  The  inspection  department's 
records  will  provide  the  excuse  for  Bill's  production  boss  to 
discuss  things  with  him  in  a  friendly  way.  Good-fellowship 
is  pretty  sure  to  result  and  the  chances  are  that  both  Bill 
and  the  factory  will  profit  as  he  begins  to  react  to  this  sort  of 
encouragement. 

I  should  hesitate  to  stress  this  thought,  in  view  of  the 
feeling  of  some  executives,  if  I  had  not  seen  the  results  in 
practice;  for  this  is  not  theory,  but  hard  fact.  We  talk  a 
great  deal  about  welfare  work  and  carry  some  of  it  into  effect 
with  very  desirable  results,  but  what  can  be  closer  to  the 
workman's  interest  than  his  regular  work?  You  must 
answer  for  yourself  whether  the  opportunities  for  building 
up  the  worker's  interest  in  what  he  is  doing  are  utilized  to 
the  full  in  the  plant  or  plants  in  which  you  are  personally 
interested.  I  do  not  refer  to  creating  " bread-and-butter" 
interest — that  is  the  usual  appeal  of  incentives  for  stimulat- 
ing production — but  rather  to  the  pride  of  good  workman- 
ship and  the  satisfaction  of  personal  achievement  which  go 
to  make  up  the  worker's  "  prof essional  pride." 

Interest  in  the  Work  Itself 

The  modern  industrial  system,  with  its  minute  division 
of  labor,  has  been  freely  criticized  for  reducing  machine 
operators  to  mere  automatons,  forced  to  eke  out  an  exist- 
ence of  tedious  and  countless  repetition  of  the  same  opera- 
tion. It  is  alleged  that  this  endless  repetition  results  in 
bodily,  mental,  and  spiritual  fatigue.  The  system  of  man- 
ufacture cannot  be  abandoned,  because  the  division  of  labor 
results  in  too  great  an  economy  of  effort  even  to  think  of  its 
elimination.  On  the  other  hand,  there  is  one  simple  but 
very  effective  corrective  measure  that  we  can  apply,  namely 


92  THE  CONTROL  OF  QUALITY 

to  encourage  the  operator's  interest  in,  and  to  excite  his 
curiosity  about,  the  work  he  is  engaged  in  doing.  Now  the 
theme  that  runs  through  this  entire  subject  is  that  quality 
is  variable,  hence  no  two  pieces  turned  out  by  any  machine 
operation  are  alike.  The  points  of  difference  may  be  com- 
paratively small,  but  to  the  eye  of  the  trained  expert  these 
same  differences  grow  to  look  much  larger  and  to  be  very 
apparent  and  real.  It  is  a  question  of  relativity  and  of 
degree. 

Expert  Knowledge — Causes  and  Results 

To  the  trained  eye  of  an  experienced  inspector  the  in- 
terior of  one  rifle  barrel  is  quite  different  from  another, 
whereas  the  greatest  difference  you  or  I  might  note,  after 
repeated  trials,  would  be  a  slightly  fuzzy  spot  resembling  a 
pencil  mark.  The  inspector  would  tell  you  that  this  barely 
distinguishable  spot  indicates  a  bad  drill  groove,  but  we 
should  not  be  at  all  certain  as  to  the  degree  of  the  defect,  its 
location,  or  even  its  existence.  In  the  course  of  time,  how- 
ever, and  with  much  repetition  we  could  learn  to  distinguish 
these  and  similar  defects  or  differences.  Things  that  ap- 
peared indistinguishably  small  at  first  would  become  of 
appreciable  size,  and  finally  they  would  take  on  individual 
characteristics.  But  the  main  point  I  wish  to  bring  out 
is  that  we  should  never  know  about  them  at  all,  if  they 
were  not  first  pointed  out  to  us  by  someone  skilled  in  their 
detection. 

Now,  the  same  thing  occurs  with  the  average  machine 
operator.  He  may  drift  along  without  noticing  the  results 
of  his  efforts  except  quantitatively.  Especially  is  it  likely 
that  he  will  have  very  little  idea  of  the  fine  points  in  the 
work  which  are  subject  to  his  control,  nor  of  the  things  he  is 
in  a  position  to  influence,  nor  why  and  how  he  can  do  so. 
It  is  no  great  trouble,  however,  for  the  inspector  (or  the 


INSPECTION'S  CONTRIBUTION  TO  SERVICE  93 

production  boss,  if  you  prefer)  to  show  him  how  each  part 
differs  a  little  from  the  next  one ;  also  what  different  kinds  of 
differences  exist  and  what  causes  them,  so  that  he  can  see 
for  himself  what  he  is  doing  qualitatively.  Thus  he  will 
learn  how  his  failure  to  clean  off  the  chips,  when  bedding  a 
piece,  throws  out  his  own  work  and  perhaps  the  next  man's, 
and  almost  certainly  makes  unnecessary  work  for  the  pol- 
isher. Or  perhaps  he  will  see  that  forcing  the  cutting  tool 
causes  him  greater  personal  loss  in  total  output  than  if  he 
used  less  apparent  speed.  The  net  effect,  however,  will  be 
the  widening  of  his  viewpoint,  the  building  up  of  an  interest 
in  his  work,  and  the  consequent  and  proportionate  lessening 
of  fatigue. 

Interest  in  Quality  versus  Fatigue 

Many  men  can  play  golf  every  day  in  the  week  including 
Sunday.  They  seem  to  enjoy  the  repetition  without  expe- 
riencing unhealthy  fatigue,  and  the  discouraging  monotony 
of  their  novitiate  is  forgotten.  The  same  thing  applies  in 
principle  in  our  daily  work,  no  matter  how  restricted  its 
field ;  if  it  is  interesting  the  resulting  fatigue  is  a  healthy  one. 
But  the  work  is  only  made  interesting  through  an  apprecia- 
tion of  its  fine  points.  It  may  take  years  of  application  to 
be  able  to  see  for  ourselves  those  fine  points  and  small  dis- 
tinctions, or  some  more  fortunate  person  may  be  kind 
enough  to  point  them  out  to  us  early  in  the  game. 

The  modern  application  of  division  of  labor  has  brought 
with  it  an  acute  problem  due  to  extreme  limitation  of  indi- 
vidual tasks,  but  the  apparent  smallness  of  the  field  of  work 
covered  by  any  one  machine  operator  can  be  changed  into 
one  of  much  greater  interest  and  wider  scope  by  suggesting 
a  different  viewpoint  to  the  workman.  The  employer 
might  well  consider  carefully  the  mutual  benefit  to  be  de- 
rived from  educating  the  worker  in  the  finer  points  of  his 


94  THE  CONTROL  OF  QUALITY 

job,  and  from  doing  so  in  a  spirit  of  friendly  helpfulness  that 
will  build  up  a  feeling  of  mutual  interest  in  a  common  task. 
The  workman  usually  is  not  capable  of  doing  it  alone,  but 
he  can  be  helped  to  do  it  by  means  of  the  regular  factory 
organization  if  the  employer  will  direct  the  foremen  toward 
this  different  attitude  in  dealing  with  their  men. 

A  Phase  of  a  Major  Problem 

It  is  suggested  that  this  is  one  way  to  help  correct  one 
of  the  major  problems  confronting  engineers,  which  Herbert 
Hoover  recently  expressed  in  the  following  language:2 

We  have  until  recently  greatly  neglected  the  human  factor  that 
is  so  large  an  element  in  our  very  productivity.  The  development 
of  vast  repetition  in  the  process  of  industry  has  divorced  the  em- 
ployer and  his  employees  from  the  contact  that  carried  responsibility 
for  the  human  problem. 

I  am  daily  impressed  with  the  fact  that  there  is  but  one  way 
out,  and  that  is  to  again  re-establish  through  organized  representa- 
tion that  personal  co-operation  between  employer  and  employee  in 
production  that  was  a  binding  force  when  our  industries  were 
smaller  of  unit  and  of  less  specialization. 

2  From  Mr.  Hoover's  presidential  address  to  the  American  Institute  of  Mining  and  Metal- 
lurgical Engineers,  Feb.  1920. 


CHAPTER  VII 
INSPECTION'S   RELATION  TO   PLANNING 

The  Flow  of  Work  in  Process 

It  is  quite  the  usual  thing  in  factory  parlance  to  use  the 
term  "flow  of  work  in  process."  More  frequently  it  is  ab- 
breviated to  "the  flow  of  work,"  or  just  "the  flow."  This 
little  expression,  which  is  used  so  readily  and  easily,  covers  a 
matter  that  is  intimately  interwoven  with  the  whole  fabric 
of  manufacturing ;  for  the  flow  of  work  is  of  the  very  essence 
of  production. 

Manufacturing  results  from  the  combination  of  labor, 
machinery,  and  material — remove  one  of  the  three  and  the 
process  ceases.  If  we  can  keep  the  flow  of  the  material 
under  control,  we  are  in  a  position  to  control  manufacturing; 
or,  as  has  been  said  many  times,  "planning  begins  and  ends 
with  material."  Thus  one  of  the  principal  aims  of  planning 
is  secured  by  arranging  for  a  continuous  supply  of  material 
to  each  production  point,  and  at  a  velocity  or  rate  of  flow 
set  to  permit  the  scheduled  output  for  that  point. 

It  would  appear  also  that  the  economy  of  manufactur- 
ing is  greatest  when  there  is  an  even  and  uninterrupted  flow 
of  work  all  along  the  line  throughout  the  factory.  Uni- 
formity seems  to  be  generally  desirable  in  manufacturing. 
Let  us  consider  some  of  the  reasons  for  this.  In  the  first 
place,  there  is  no  advantage  gained  by  pushing  one  opera- 
tion ahead  of  the  average  scheduled  rate  of  production. 
The  average  rate  at  which  completelyassembled  mechanisms 
can  be  produced,  and  hence  the  average  output  of  finished 
articles,  is  fixed  by  the  average  output  of  that  component 
part  which  lags  most  in  the  manufacture.  In  fact,  the  rate 

95 


96 


THE  CONTROL  OF  QUALITY 


INSPECTION'S  RELATION  TO  PLANNING  97 

of  total  output  is  determined  by  the  rate  of  flow  of  work 
through  the  single  manufacturing  operation  or  process  that 
is  lagging — "The  speed  of  the  fleet  is  the  speed  of  the 
slowest  ship." 

Uneven  Flow — Disadvantages 

When  assembling  is  permitted  to  proceed  more  rapidly 
than  parts  can  be  produced,  it  soon  eats  up  the  available 
reserve  of  parts  and  a  famine  results,  with  its  accompanying 
pressure  on  the  parts-producing  shops.  The  first  effect  of 
too  great  pressure  for  quantity  output  is  psychological — 
it  amounts  in  practice  to  "getting  everybody  all  worked 
up."  The  same  thing  happens  when  the  train  stops  at  an 
eating  place— " twenty  minutes  for  dinner — lots  of  time." 
All  of  us  know  what  an  iron  nerve  it  takes  not  to  hurry 
through  with  the  job  in  half  the  time,  at  the  expense  of  both 
appetite  and  digestion.  When  unusual  pressure  is  placed 
on  a  shop  the  foremen  stand  over  the  men  and  hurry  things 
along,  with  the  net  result  of  less  output  and  of  poorer  qual- 
ity. When  a  factory  is  run  in  this  manner  the  cost  of  in- 
spection for  maintaining  the  set  standards  is  much  greater 
than  it  need  be  under  more  normal  conditions.  In  the  same 
way  other  indirect  expenses  are  increased  disproportion- 
ately. Thus  transportation  of  work  in  process  is  much  less 
expensive  if  carried  on  at  a  uniform  rate,  instead  of  being 
turned  into  the  movement  of  many  small  lots  of  parts  as 
soon  as  they  are  produced. 

The  ideal  plan  is  so  to  protect  the  flow  of  work  as  to  have 
fixed  or  schedu'ed  quantities  passing  each  production  point 
during  each  unit  of  time.  Unless  we  approximate  to  this 
ideal  within  reasonable  limits,  we  shall  have  less  production 
and  at  the  expense  of  undue  strain  of  the  producers.  When 
real  emergencies  occur  they  should  find  the  organization 
fresh  and  ready  to  meet  them. 


98  THE  CONTROL  OF  QUALITY 

Effects  on  Piece  Work 

Another  serious  defect  resulting  from  an  uneven  flow  of 
work  arises  from  the  fact  that  the  continuous  use  of  piece 
work  is  interfered  with.  Everyone  knows  that  the  output 
under  a  straight  piece  work  or  other  system  of  payment 
based  upon  paying  a  man  for  what  he  does,  is  very  much 
greater  than  when  the  man  is  paid  for  his  time,  on  a  day- 
wage  basis.  But  the  advantages  of  piece  work  cannot  be 
fully  realized  unless  there  is  a  supply  of  material  waiting  at 
each  machine  for  that  particular  operation.  If  there  is  a 
hitch  in  the  chain  of  supply,  workmen  are  soon  to  be  seen 
standing  round  waiting  for  material  to  work  on.  It  is  not 
their  fault,  and  they  must  be  paid  "day-work"  for  any 
appreciable  loss  of  working  time  imposed  upon  them. 

Supply  of  Raw  Materials 

Approaching  the  question  from  a  different  angle,  we  may 
note  a  similarity  of  situation  in  the  supply  of  raw  material. 
A  prompt  and  continuous  supply  is  always  important,  but 
during  the  war  the  procurement  of  material  and  supplies 
in  the  order  and  in  the  amounts  required  for  continuous 
production  assumed  serious  proportions.  In  the  ship- 
building business  especially,  this  matter  of  procurement 
took  on  a  new  value,  and  it  is  a  safe  statement  that  the 
speed  of  building  in  any  yard  was  determined  first  and  to 
a  controlling  degree  by  the  efficiency  of  the  preplanning  for 
this  purpose. 

Even  if  the  size  of  a  factory's  raw  material  storehouses 
and  storage  spaces  were  not  influenced  by  a  desire  to  be  able 
to  take  advantage  of  favorable  market  conditions,  it  still 
would  be  necessary  to  set  aside  the  space.  A  stock  must  be 
accumulated  against  possible  failures  in  delivery,  in  order 
that  machines  may  not  have  to  be  shut  down  for  lack  of 
something  to  work  upon. 


INSPECTION'S  RELATION  TO  PLANNING  99 

Material  in  Process 

The  identical  principle  applies  to  providing  a  supply  or 
"bank"  of  material  ahead  of  each  manufacturing  operation 
or  production  point,  although  this  fact  is  not  so  generally 
appreciated.  A  proper  flow  of  work  can  hardly  be  main- 
tained with  less  than  a  half-day's  supply  ahead  of  each 
operation,  although  the  amount  of  work  in  each  bank  is 
governed  by  local  conditions.  It  is  understood  that  the 
French  small-arms  arsenals  were  eminently  successful  in 
obtaining  large  output  of  high  quality  under  very  trying 
conditions;  also  that  it  was  the  practice  to  keep  at  least  a 
day's  supply  of  work  (and  two  days'  if  practicable)  ahead  of 
each  operation. 

Breakdowns  of  equipment  and  other  troubles  are  bound 
to  develop  choke-points  from  time  to  time,  and  an  unbroken 
flow  can  only  be  insured  by  building  up  and  maintaining 
reserves  all  along  the  line.  These  banks  of  material  can 
then  be  drawn  upon  as  needed  to  keep  the  machines  going 
ahead  of  the  choke-point,  until  the  production  point  that  is 
in  trouble  is  restored  to  running  condition.  Then  the  re- 
serves can  be  again  accumulated  by  extra  shift  work. 

From  this  point  of  view,  there  is  a  bank  between  the 
assembling  room  and  the  parts-making  shops  in  the  form  of 
a  finished  component  stores,  which  bears  the  same  relation 
to  the  assembling  department  that  the  raw  material  stores 
bears  to  the  parts-fabricating  shops. 

The  quantity  of  parts  to  be  kept  in  each  bank  depends, 
of  course,  on  the  likelihood  of  trouble  at  preceding  opera- 
tions, or  other  interruptions  to  production.  For  example, 
if  it  is  probable  that  changes  in  design  or  method  of  manu- 
facture are  to  be  made,  it  must  be  remembered  that  a  change 
of  any  sort  means  a  serious  interruption  in  the  flow  of  work. 
To  handle  the  situation,  when  a  change  must  be  made, 
requires  special  treatment  in  each  case,  and  calls  for  masterly 


100  THE  CONTROL  OF  QUALITY 

planning  of  the  highest  order.     It  is  economy  to  take  the 
time  to  do  this  planning  before  carrying  out  the  change. 

Insuring  a  Continuous  Flow 

The  effect  of  a  breakdown  in  production  can  be  mini- 
mized at  times  by  providing  the  factory  with  a  chart  show- 
ing approved  alternative  routings  of  the  work.  It  is  not 
safe,  however,  to  route  work  more  than  two  ways  simul- 
taneously, especially  if  there  are  many  parts  in  flow.  Special 
care  should  be  taken  when  two  routes  are  used  to  keep  dis- 
tinct the  work  sent  over  each  route,  and  in  this  effort  the 
inspection  department  can  be  of  the  greatest  assistance. 

Similarly,  the  inspection  department,  in  its  regular  task 
of  sorting  out  the  defective  parts,  makes  a  large  contribu- 
tion to  promoting  a  uniform  flow  of  work,  for  it  is  essential 
from  the  standpoint  of  protecting  the  flow  that  rejected  and 
condemned  work  be  disposed  of  swiftly  and  promptly  re- 
moved from  the  shop. 

The  control  of  supplies  of  material  and  of  banks  of  work 
in  process,  and  therefore  the  control  of  the  flow  of  work 
throughout  the  factory,  is  greatly  simplified  if  there  is  a 
systematic  storage  of  work  in  process.  This  result  cannot 
be  secured  by  planning  on  paper  alone,  no  matter  how  com- 
pletely and  extensively  this  planning  is  done.  The  work 
itself  should  be  distributed  in  such  a  definite  and  orderly 
manner  (and  in  a  shop  swept  clean  of  everything  not  used  in 
the  business)  that  the  condition  of  the  flow  can  be  vizualized 
by  looking  at  the  work — without  reference  to  paper  rec- 
ords. This  brings  us  to  a  matter  which  deserves  special 
consideration. 

Planning  with  the  Material  Itself 

In  order  to  treat  this  matter  thoroughly,  it  is  necessary 
to  trace  the  steps  that  must  be  taken  to  reach  a  position 


INSPECTION'S  RELATION  TO  PLANNING  IOI 

where  planning  with  the  material  in  process  is  possible. 
Planning,  in  the  broadest  sense  in  which  the  term  is  used, 
has  developed  certain  mechanisms  in  addition  to  its  first 
work  of  preplanning  the  routing  of  work.  Thus  it  must  be 
considered  as  inclusive  of  the  preparing  of  schedules  of 
quantities  of  work  to  be  produced  at  given  times ;  and  of  the 
dispatching  of  work  at  rates  in  conformity  with  these  sched- 
ules. To  this  will  now  be  added  the  planning  of  space 
assignments  for  work  in  process. 

Only  the  high-spots  can  be  touched  upon,  with  reference 
to  the  details  involved  in  such  planning,  but  that  is  really 
all  that  is  necessary,  because  the  other  details  will  readily 
suggest  themselves  when  the  general  scheme  is  applied  to 
a  concrete  case.  It  should  be  kept  in  mind  concurrently 
that  the  inspection  department  can  be  made  the  principal 
instrument,  and  a  most  economical  one,  in  giving  life  to  the 
planning  department's  work,  when  the  time  comes  to  trans- 
late plans  into  action. 

Master  Planning 

Let  us  assume  now  that  an  article  has  been  designed  and 
is  ready  for  manufacture,  and  that  the  planning  force  is  called 
upon  to  preplan  for  producing  and  bringing  to  assembly 
given  quantities  of  parts  which  meet  certain  stated  standards 
of  quality,  and  for  assembling  these  parts  into  the  complete 
articles.  It  is  assumed  at  the  outset  that  the  management, 
in  conference  with  the  principal  department  heads,  has 
developed  and  approved  a  general  plan  for  carrying  out  the 
project;  also  that  this  plan  has  been  drawn  up  by  the  plan- 
ning department  in  the  form  of  a  master  control  sheet  or  sheets 
for  the  guidance  of  all  concerned.  Among  the  data  shown 
thereon  would  be  a  list  of  the  things  to  be  done  (i.e.,  the 
whole  project  is  analyzed  into  its  parts),  the  department  or 
individual  responsible  for  carrying  out  each  part  of  the 


/\H/i  Clff'f!   !  «v*.I  * 

102  THE  CONTROL  OF  QUALITY 

work,  and  the  time  when  each  part  of  the  work  should  be 
started  and  completed  in  order  to  secure  co-ordination  of  all 
the  parts. 

As  the  drafting-room  takes  up  the  making  of  working 
drawings  and  special  tool  designs,  the  planning  department 
in  co-operation  with  the  drafting-room  should  make  up  a 
complete  list  of  parts  and  subassemblies,  together  with  the 
tentative  outlines  of  bills  of  material,  which  last  may  later 
be  entered  on  the  appropriate  plans.  The  first  draft  of 
material  requirements  is  then  taken  off  for  the  guidance  of 
the  purchasing  department  and  the  storeskeeper,  so  that 
they  may  make  their  preliminary  arrangements. 

The  Operation  Mark  or  Symbol 

With  a  complete  list  of  component  parts  and  subassem- 
blies in  hand,  it  now  devolves  upon  the  planning  department 
to  devise  and  apply  a  set  of  symbols,  as  some  such  device  is 
a  sine  qua  non  to  an  orderly  and  systematic  control  of  the 
flow  of  work.  If  the  factory  does  not  have  a  satisfactory 
symbol  system  already  it  is  suggested  that  a  combination  of 
figures  and  letters  may  be  used  to  advantage. 

In  building  up  such  a  scheme  of  symbolization  it  is  im- 
portant to  distinguish  between  the  symbol  for  a  particular 
manufacturing  operation,  and  the  number  which  indicates 
the  order  or  sequence  in  which  the  operation  is  to  be  per- 
formed. Such  an  operation  may  be  defined  as  meaning  any 
one  application  of  a  mechanical  or  other  process  in  the 
course  of  making  some  one  part.  Drilling  is  a  mechanical 
process.  Drilling  a  hole  for  the  hinge-pin  in  the  shackle 
of  a  given  model  of  a  lock  is  an  operation.  In  this  case 
the  mechanical  equipment  for  the  operation  would  be  a 
light  drill  press,  drills,  a  drill  jig,  and  a  limit  plug  gage. 

The  first  layout  for  processing  the  job  of  making  this  lock 
shackle  might  list  the  drilling  of  the  hole  as  the  fourth  opera- 


INSPECTION'S  RELATION  TO  PLANNING  103 

tion  to  be  performed  on  the  pieces.  Later  on,  the  order  of 
processing  might  be  changed  to  permit  of  improvement,  or 
for  some  other  equally  good  reason.  A  way  might  be  found 
to  eliminate  some  of  the  earlier  operations,  or  additional 
operations  might  have  to  be  inserted,  so  that  the  operation 
of  drilling  the  hole  might  become  perhaps  the  third,  perhaps 
the  tenth  in  order  of  sequence.  Now  it  is  of  considerable 
value  to  have  some  one  permanent  mark  or  symbol  for  des- 
ignating the  operation  of  drilling  this  hole,  if  for  no  other 
reason  than  cost-keeping.  In  shops  where  the  attempt  is 
made  to  make  one  symbol  do  for  indicating  both  the  opera- 
tion and  its  sequence,  the  cost  of  operation  No.  1103  may 
cover  drilling  this  month  and  grinding  next  month.  Con- 
sider the  effect  on  the  tool  storage  and  supply  system  alone, 
as  well  as  on  all  quantity  and  quality  records. 

Operation  Mark  to  Remain  Unchanged 

It  is  to  be  understood  then,  that  the  operation  mark 
is  assigned  once  and  for  all  to  a  given  operation,  and  never 
changed.  If  the  operation  is  abandoned,  so  is  the  operation 
mark.  If  there  are  twenty  operations  in  making  a  part 
and  it  is  found  necessary  to  provide  another  operation,  the 
new  one  is  marked  as  the  twenty-first,  without  reference  to 
the  place  where  it  is  inserted  in  the  list  of  operations.  This 
mark  is  then  used  in  correspondence,  on  plans,  in  marking 
tools,  tool  storage  bins,  and  so  on,  wherever  and  whenever  it 
is  necessary  to  refer  to  the  operation  or  anything  connected 
with  it.  As  stated  before,  no  attempt  is  made  to  make  this 
symbol  designate  the  sequence  of  the  operation's  application. 
The  matter  of  sequence  is  covered,  when  necessary,  by  a 
separate  number  entirely  divorced  from  the  operation  mark ; 
but  the  sequence  number  as  such  is  not  required  to  anything 
like  the  extent  that  the  mark  is.  When  the  operations  are 
listed,  a  separate  column  should  be  provided  for  entering 


104  THE  CONTROL  OF  QUALITY 

the  sequence  number  for  each  operation ;  and  a  corrected 
list  should  be  furnished  for  the  guidance  of  the  shop  when 
changes  are  made  in  the  order  of  performance  of  operations. 
If  route  tags  are  used  with  each  lot  of  parts,  the  sequence  is 
indicated  by  the  order  in  which  the  operation  marks  are 
listed,  or  the  sequence  numbers  may  be  printed  opposite  the 
corresponding  marks.  (See  Figure  19,  page  108.) 

This  scheme  for  symbolizing  applies  to  the  factory  prod- 
uct, its  component  parts,  the  operations  used  in  manufac- 
turing them,  and  the  equipment  strictly  related  to  such 
operations.  It  does  not  apply  to  the  symbol  system  used 
for  designating  parts  of  the  factory  itself,  or  the  machine  tool 
equipment,  which  should  be  provided  for  separately.  If 
you  have  a  system  in  use  which  is  giving  reasonable  satisfac- 
tion, by  all  means  use  it  in  the  shops  as  well  as  in  the  office, 
the  important  point  being  that  something  of  the  sort  is 
necessary  to  bring  order  out  of  chaos  and  to  permit  a  sys- 
tematic and  orderly  arrangement  of  work  in  process. 

The  Operation  Data  Sheet 

The  next  step  in  planning  involves  the  assembling  of  all 
the  information  the  shops  should  have  relative  to  the  proc- 
essing that  is  to  be  followed  in  manufacturing  the  parts  and 
putting  them  together.  It  is  suggested  that  an  operation 
study  sheet  of  standardized  form  (see  Figure  17)  be  used  in 
developing  and  recording  the  process  information  for  each 
part,  and  that  from  this  there  be  compiled  an  operation  data 
sheet  (Figure  18)  for  shop  use. 

It  is  believed  that  the  preceding  discussion,  relative  to 
the  distinction  between  the  sequence  of  an  operation  and  its 
distinctive  mark  or  symbol,  will  make  clear  the  data  to  be 
entered  on  this  sheet.  All  the  machine  tool  equipment 
will  be  labeled  or  otherwise  suitably  numbered  and  marked 
for  inventory  purposes  at  any  rate,  and  these  individual 


INSPECTION'S  RELATION  TO  PLANNING 


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THE  CONTROL  OF  QUALITY 


machine  numbers  may  be  entered  on  the  operation  data 
sheet,  if  additional  clearness  is  required. 

Special  tests  should  be  entered  as  separate  operations. 
Inspection  points  may  be  mentioned  in  like  manner,  or  re- 
ferred to  by  some  designating  mark,  or  left  out  altogether, 
depending  on  the  character  and  relative  complexity  of  the 
work.  Operation  data  sheets  should  be  made  out  for  each 
subassembly,  and  for  the  final  assembly,  just  as  in  the  case 
of  each  component  part. 

A  similar  sheet  showing  alternative  routings,  or  sequences 

of  operations  to  be  followed 
in  case  of  emergency,  may 
be  developed  for  each  part ; 
but  as  these  will  not  be  used 
frequently,  it  is  probably 
simpler  and  better  practice 
to  show  this  information 
in  chart  form. 


Pifces                        0             8°BB1 
Order  No.                                 Lot  No. 

DATE 

EMP. 
NO. 

OPERATION 

OPER. 
MARK 

Swage  Catch  Hole 

49 

Shop          £-7-7              I      out 

in 

File  T  Slot  Burr  Catch  Hole 

50 

Shop          B-2                I     out 

In 

R.Pol.SideEnd&CornerPom. 

41 

Cut  Down  Under  Pom. 

86 

Fin.LtSide,Under&Chamfer 

158 

Shop          C-1-1            I     out 

In 

Corner  Slot.Mill 

87 

Corner  Slot  File 

88 

Shop          £-7-7             1     out 

In 

Assemble  and  Fit  Catch 

51 

Shop          B-2               1     out 

in 

Rough  Polish  Edge  Guard 

89 

Rough  and  Finish  Pol.  Pom. 

166 

Rough  and  Finish  Pol.  Guard 

167 

Pol.  for  Gage 

61 

Shop           B-7-7             fl     out 

In 

Edge 

67 

Finish  Points 

162 

Shop          c-1               II     out 

In 

Fit  to  Gage 

53 

Stamp 

66 

Brown 

56 

Shop           C-B               ||     out 

In 

Sand  Blast 

58 

Shop          E-1                1     out 

in 

Wash  and  Oil  Pom. 

59 

Assemble  Grip 

60 

Straighten  Tang 

68 

SwedgeTSlot 

63 

Shoo         B-3 

Figure 


19.     Route    Tag — Remington 
Arms  Company 


Route  Tags 

From  the  operation 
data  sheet  it  is  a  simple 
matter  to  work  up  printed 
route  tags,  if  these  are  re- 
quired, to  go  with  each  lot 
of  parts.  Under  the  system 
proposed,  no  mention  of  the 
sequence  of  operations  need 
be  made,  as  this  will  be  cov- 
ered by  the  order  in  which 
the  operations  are  listed. 
The  data  taken  from  the 
operation  data  sheet  for  in- 
corporation in  the  route  tag 


INSPECTION'S  RELATION  TO  PLANNING  109 

then  consists  only  of  the  shop  symbol  or  name,  and  the 
operation  mark  or  symbol.    (See  Figure  19.) 

The  route  tag,  and  in  fact  all  planning  work,  will  be 
simplified  if  shops  are  designated  by  number  or  letter  rather 
than  by  name.  A  simple  but  effective  plan  is  to  assign  a 
letter  to  each  building;  to  number  the  floors,  beginning  with 
the  basement  as  No.  i ;  and  then  add  a  letter  to  locate  the  part 
of  the  floor  according  to  compass  direction. 

The  Manufacturing  Schedule 

In  tracing  the  steps  to  be  taken  by  the  planning  depart- 
ment in  order  to  reach  a  point  where  planning  with  material 
is  possible,  it  now  becomes  necessary  to  work  out  the  daily 
or  weekly  production  schedule,  upon  which  the  design  of 
the  space  assignments  for  material  in  process  is  to  be  based. 
Suppose  the  production  schedule  contemplates  an  output  of 
1,000  complete  articles  during  each  working  day.  This 
means  that  somewhat  more  than  a  thousand  of  most  of  the 
component  parts  must  be  produced  daily,  for  the  reason 
that  a  few  will  be  spoiled  in  the  assembling  department,  or 
for  some  other  reason  will  cease  to  be  available.  Then  in 
the  case  of  each  part,  this  quantity  of  1 ,000 +n  pieces  must  be 
increased  by  the  estimated  losses  at  each  operation  as  we 
trace  it  back  through  the  various  steps  in  its  manufacture, 
so  that  material  for  perhaps  1,200  pieces  of  the  part  in  ques- 
tion must  be  started  into  production  at  the  first  operation 
each  day,  in  order  to  maintain  the  schedule  with  certainty. 

Allowance  for  Losses  in  Process 

The  losses  at  each  operation  which  are  allowed  in  pre- 
planning, should  be  checked  in  practice  by  comparison  with 
reports  supplied  to  the  planning  department  by  the  inspec- 
tion department.  The  importance  of  making  an  adequate 
allowance  for  loss  of  work  in  process  should  be  realized  and 


110  THE  CONTROL  OF  QUALITY 

it  may  be  noted  at  this  place  that  the  percentage  of  loss  for 
most  economical  production  at  each  important  operation 
may  be  worked  out  quantitatively  for  the  planning  depart- 
ment by  the  inspection  department  as  the  work  proceeds. 
The  inspection  department,  for  example,  may  tighten  up  or 
loosen  up,  on  such  part  of  the  work  as  it  is  in  a  position  to  in- 
fluence by  its  personal  judgment  (i.e.,  work  that  is  question- 
ably close  to  the  limits) ;  and  then  report  back  to  the  planning 
department  the  total  production  and  totals  of  rejected  work 
corresponding  to  the  different  degrees  of  inspection  applied 
in  the  tests.  It  is  then  up  to  the  planning  department  to 
compute  the  corresponding  total  costs,  including  losses,  and 
set  the  standard  percentage  of  loss  to  which  the  inspection 
department  should  hold  the  work  in  order  to  recover  the 
greatest  economy  in  production.  This  percentage  loss 
may  be  reduced  later  when  improvements  in  workman- 
ship and  equipment  warrant. 

The  production  schedule  just  referred  to  is  for  a  uniform 
flow  and  therefore  should  be  supplemented  by  a  gradually 
increasing  schedule  for  use  in  starting  into  production.  A 
similar  schedule  should  be  used  in  tapering  off  production 
to  prepare  for  changing  models. 

Determining  Quantities  of  Work  in  Flow 

The  planner  is  now  in  a  position  to  prepare  a  table  show- 
ing the  quantities  of  work  to  be  provided  in  the  banks  of 
material  at  each  stage  of  manufacture  in  order  to  insure  a 
continuous  flow  of  work.  In  brief  but  complete  form 
this  will  include: 

1.  The  maximum  and  minimum  quantity  of  raw  ma- 

terial to  be  carried  in  raw-stock  stores  for  each 
part. 

2.  For  each  operation  the  minimum  quantity  of  ma- 

terial in  process  waiting  for  the  next  operation. 


INSPECTION'S  RELATION  TO  PLANNING  III 

The  maximum  quantity  should  be  specified,  but  is 
not  of  great  importance. 

3.  The  minimum  and  maximum  quantity  of  finished 
parts  to  be  carried  in  the  finished-parts  stores  as  a 
bank  between  the  producing  shops  and  the  assem- 
bling department,  including  similar  data  far  sub- 
assemblies. 

These  assumed  quantities  will  be  adjusted  later  to  bring 
them  into  accord  with  the  conditions  as  they  develop  after 
production  is  under  way. 

There  is  no  exact  rule  that  can  be  followed  in  fixing 
upon  the  maximum  and  minimum  quantities  of  parts  to  be 
carried  in  the  banks  of  work  in  process.  Generally  speaking, 
it  is  safe  to  allow  a  day  for  any  one  piece  to  pass  each  opera- 
tion, and  therefore  it  is  well  to  provide  for  a  minimum  supply 
of  a  half-day's  work,  and  a  maximum  of  from  one  to  two 
days'  work,  depending  upon  the  local  conditions. 

The  Design  of  Space  Assignments  for  Planning  with  Material 
It  is  now  proposed : 

1 .  That  the  table  of  quantities  of  material  required  at 

each  operation, in  order  to  maintain  uninterrupted 
flow,  be  used  as  a  guide  to  compute  the  space  re- 
quired to  store  each  maximum  quantity. 

2.  That  layout  plans  be  made  for  each  shop,  on  which 

a  definite  space  is  assigned  to  each  such  bank  of 
material,  in  the  same  way  as  machines  are  shown. 

3.  That  the  space  so  assigned  be  designated  in  physical 

form,  if  the  class  of  work  will  permit  (and  it 
usually  will),  e.g.,  by  boundary  lines  on  the  floor. 

4.  That  each  space  so  assigned  have  the  symbol  marked 

thereon,  and  that  the  maximum  and  minimum 
quantities  either  be  shown  in  figures  or  at  least  be 
readily  accessible  for  reference. 


112  THE  CONTROL  OF  QUALITY 

This  contemplates,  it  will  be  observed,  an  extension  of  the 
best  factory  raw-material  storeroom  practice  to  the  storage  of 
material  in  process  in  the  shop.  This  is  for  the  purpose  of 
reaping  the  advantage  accruing  both  to  quality  and  quan- 
tity of  output  by  keeping  work  in  process  under  positive 
control  at  all  times  and  places. 

The  objection  most  frequently  advanced  against  such  a 
plan  is  that  there  is  not  enough  room  in  the  shop.  As  against 
this  view,  it  is  submitted  that  there  is  always  more  room 
when  things  are  systematically  arranged.  But  to  carry  out 
an  orderly  arrangement  of  work,  it  should  be  borne  in  mind 
that  it  is  idle  to  try  to  have  everything  in  its  proper  place, 
unless  the  proper  place  in  question  is  clearly  indicated. 
This  last  is  no  difficult  matter.  It  is  a  common  practice  to 
paint  aisle  lines  on  the  shop  floor,  and  what  is  proposed  is 
merely  an  extension  of  this  scheme. 

For  example,  if  the  shop  building  is  wide  there  probably 
is  a  space  in  the  center  which  is  not  well  lighted.  This  space 
can  be  ruled  off  for  the  orderly  storage  of  work  in  process. 
Or  the  best  arrangement  may  be  to  utilize  spaces  between 
machines,  or  next  to  columns,  or  possibly  under  the  windows. 

With  the  added  refinement  of  having  the  quantities  to 
be  carried  in  these  storage  spaces  either  marked  near  them, 
or  otherwise  made  readily  accessible,  it  is  possible  to  walk 
through  the  shop  and  observe  the  condition  of  the  flow  of 
work  without  the  necessity  of  resorting  to  paper  records  to 
discover  how  things  stand.  It  is  exactly  comparable,  in 
principle,  to  checking  up  the  stock  of  a  well-arranged  store- 
room by  a  simple  visual  inspection.  For  practical  purposes, 
it  has  the  great  merit  of  speed.  You  do  not  have  to  wait  to 
find  out  what  you  need  to  know. 

This  is  what  is  meant  by  " planning  with  material" — a 
term  here  used  to  distinguish  the  method  from  planning  on 
paper,  which  process  it  extends  and  supplements.  It  rep- 


INSPECTION'S  RELATION  TO  PLANNING  113 

resents  indeed  a  culminating  point  in  the  system  work  of 
planning. 

Inspection  and  Dispatching 

Let  us  assume  now,  that  we  have  an  orderly  condition  of 
things  in  the  shop,  and  that  the  inspection  force  is  reason- 
ably efficient  and  on  the  job.  No  very  great  additional 
burden  will  be  placed  on  the  inspectors  if  they  are  given  the 
added  task  of  the  custody  of  work  in  process.  The  inspector 
will  see  that  work  is  moved  to  the  next  bank  (or  operation 
storage  space)  as  soon  as  it  has  been  passed  by  him.  Con- 
currently, the  inspector  will  assist  in  dispatching  work  in 
accordance  with  the  schedules. 

When  the  flow  gets  out  of  balance  at  some  point  it 
devolves  upon  the  inspector  to  direct  the  production  depart- 
ment's attention  to  the  fact  if  the  foreman  is  not  already 
aware  of  the  situation.  If  the  condition  is  a  serious  one, 
and  a  bad  choke-point  is  resulting  therefrom,  the  produc- 
tion department  may  resort  to  overtime  work,  or  prefer- 
ably to  the  use  of  an  extra  shift.  There  is  nearly  always 
work  for  such  a  balancing  shift  of  all-round,  or  " handy," 
machine  operators  to  help  maintain  a  uniform  flow  in  a  large 
factory. 

Doubtless  there  are  many  other  methods  for  controlling 
the  flow  of  work.  At  one  time  I  visited  a  factory  in  which 
the  flow  was  controlled  by  limiting  the  daily  output  of  the 
fastest  operators,  although  the  superintendent  did  not  so 
designate  the  process.  He  stated  that  on  certain  operations, 
which  were  indicated,  the  workmen  were  through  with  their 
day's  work  when  they  had  completed  a  fixed  number  of 
pieces,  and  that  this  made  it  a  very  simple  matter  to  keep 
the  slower  operations  from  being  swamped.  Surely  this 
is  a  simple  and  direct  method  of  insuring  a  balanced  con- 
dition of  flow,  but  how  about  its  reaction  on  the  whole 


114  THE  CONTROL  OF  QUALITY 

matter  of  production?  The  inspection  force  was  available, 
and  could  have  been  utilized,  under  a  properly  organized 
plan,  to  keep  the  shop  in  balance  as  well  as  in  a  far  more 
orderly  and  workmanlike  condition,  without  stopping  work 
at  any  process. 


CHAPTER  VIII 
CENTRAL   INSPECTION 

The  Most  Advanced  Form  of  Inspection 

The  greatest  possibilities  of  controlling  the  flow  of  work 
in  process,  by  planning  with  the  material  itself,  are  realized 
when  conditions  permit  that  inspection  be  centralized  and 
physically  separated  from  the  rest  of  the  shop.  Further- 
more, the  control  of  both  production  and  inspection  reaches 
its  highest  development  under  this  system.  While  central 
inspection  is  the  most  highly  specialized  form  of  inspection, 
its  use  need  not  be  so  restricted  as  might  appear.  For  work 
that  is  done  in  large  volume,  central  inspection  provides  by 
far  the  best  means  for  controlling  manufacturing  conditions. 
This  statement  holds  good  even  if  the  amount  of  inspection 
to  be  performed  is  relatively  small,  because  central  inspec- 
tion provides,  in  addition  to  the  inspection  feature,  a  better 
chance  to  issue  work  and  record  individual  production  in  an 
orderly  and  accurate  way. 

Not  Restricted  to  One  Form 

Central  inspection  may  take  many  forms,  and  is  not  re- 
stricted in  its  application  to  the  business  of  making  small 
interchangeable  parts  in  quantity.  The  basic  principle  of 
widest  application  is  that  of  physically  separating  inspec- 
tion from  production.  In  the  weave  shed  of  a  textile  plant, 
for  example,  there  would  natually  be  some  sort  of  inspection 
or  patrolling  supervision  of  the  work  on  the  looms.  Central 
inspection  would  hardly  be  looked  for.  Yet  the  practice  of 
removing  the  goods  to  a  separate  inspection  room  after 
weaving  (where  they  are  rerolled,  measured,  graded  accord - 

115 


Il6  THE  CONTROL  OF  QUALITY 

ing  to  quality,  and  the  defects  indicated  by  some  system  of 
marking)  is  nothing  if  not  centralized  inspection.  (See 
Figure  43.)  It  will  be  apparent  from  the  following  that  the 
principle  can  be  extended  to  embrace  many  different  sorts  of 
work,  with  all  the  advantages  from  the  more  special  use  of 
central  inspection  in  strictly  interchangeable  manufacturing. 
A  natural  restriction  to  the  application  of  central  inspec- 
tion is  encountered  when  the  work  is  too  bulky  or  too  heavy 
to  warrant  moving  except  from  machine  to  machine.  Never- 
theless, it  should  be  noted  that  central  inspection  can  be 
used  for  much  larger  and  heavier  work  than  is  ordinarily 
supposed  to  be  the  case,  provided  full  use  is  made  of  modern 
handling  devices.  For  example,  large  military  rifle  stocks, 
which  are  heavy  and  bulky  in  the  earlier  stages  of  manu- 
facture, have  been  handled  in  shops  under  central  inspec- 
tion, by  transporting  them  in  lots  of  as  many  as  40.  In  this 
case,  they  were  carried  in  a  double  rack  mounted  on  large 
casters.  Other  large  and  heavy  parts  are  often  carried  on 
lifting  truck  platforms,  designed  to  carry  a  definite  number. 

Value  of  Self-Counting  Trays 

The  use  of  special  carrying  trays  of  the  self-counting 
variety  should  be  extended.  They  are  inexpensively  made 
of  wood,  protect  the  pieces  from  damage,  and  save  much 
time  in  counting  work.  For  example,  suppose  the  problem 
is  to  provide  means  for  handling  in  quantity  a  part  approxi- 
mating T  in  shape — a  shape  which  typifies  the  general  form 
of  many  parts.  In  the  earliest  operations  of  its  processing, 
it  may  be  handled  in  bulk  in  ordinary  metal  tote  boxes,  hold- 
ing, say,  200  pieces.  As  the  processing  advances,  opera- 
tions are  encountered  that  remove  metal  down  to  or  near 
the  finished  surfaces.  It  is  now  an  economy  to  keep  the 
pieces  from  injuring  each  other.  Carriers  should  be  made, 
preferably  of  shellacked  wood,  of  rectangular  form  to  sup- 


CENTRAL  INSPECTION  117 

port  ioo  parts,  in,  say,  10  rows  of  10  pieces  each,  and  ar- 
ranged to  permit  stacking. 

The  objection  to  open  bottom  containers  of  this  type  is 
that  oily  work  drains  onto  the  floor,  but  most  of  this  trouble 
can  be  avoided  by  providing  a  draining  pan  under  the  tray 
of  work  at  the  machine.  As  just  stated,  tote  boxes  of  this 
character  serve  a  very  useful  purpose  in  assuring  a  finer  fin- 
ish by  protecting  parts  from  the  little  scratches,  dents,  and 
cuts  that  so  detract  from  quality.  Their  principal  value, 
however,  flows  from  the  self-counting  feature,  which  sim- 
plifies the  labor  of  securing  an  accurate  count,  and  does 
away  with  arguments  as  to  the  number  of  pieces  issued  to, 
or  received  back  from  the  machine  operator.  Central  in- 
spection almost  necessitates  something  of  the  sort  to  develop 
its  greatest  possibilities. 

In  this  connection  attention  is  invited  to  Edward  H. 
Tingley's  article  on  "  Making  the  Truck  an  Asset  in  Man- 
agement,"1 from  which  the  following  is  quoted  (see  also 
Figures  20  to  23  inclusive  from  the  same  article) : 

SPEEDING  UP  THE  WORK  OF  OPERATORS,  INSPECTOR,  AND 
STOREKEEPER.  The  workman  expects  any  system  for  handling 
material  to  help  him  increase  his  productive  capacity  as  well  as 
decrease  his  effort.  The  special  trucks  illustrated  have  these  ad- 
vantages, as  they  occupy  a  minimum  of  floor  space  and  allow  the 
work  to  be  brought  as  close  as  possible  to  the  machine.  The  trucks 
are  easily  moved  by  one  man,  and  with  work  stacked  on  both  sides 
they  can  be  turned  around  to  bring  the  other  side  to  the  machine, 
thus  eliminating  useless  walking.  The  construction  of  the  truck  in- 
sures the  separation  of  the  pieces  and  so  prevents  damage  to  any 
finished  or  ground  surfaces.  It  also  suggests  the  idea  of  order  and 
care  to  the  workman,  and  it  gives  him  the  satisfaction  of  seeing  his 
work  progress.  He  unconsciously  sets  a  goal  for  himself,  endeavor- 
ing to  complete  a  row  or  truck  by  noon  or  night.  The  amount  on 
the  truck  is  proportioned  to  what  one  man  can  push  around  and 
also  what  will  make  a  good  quantity  for  piecework  operations. 


1  Management  Engineering,  Nov.  1921. 


118 


THE  CONTROL  OF  QUALITY 


CENTRAL  INSPECTION 


119 


The  work  of  the  inspector  should  be  as  limited  as  possible,  as  his 
work  is  indirect  labor,  an  item  of  overhead  expense.  In  any  well- 
regulated  factory  the  foreman  should  be  fully  responsible  for  the 


Figure  21. 


A  Wood  Frame  Truck 

handling  the  armatures  when 


This  type  is  used  in  the  armature  department  fo 

complete. 


quality  of  work  produced,  and  the  inspector  should  merely  check  the 
foreman.  If  the  truck,  box,  or  rack  in  which  the  material  is  handled 
will  permit  of  quick  and  accurate  counting  by  the  inspector,  easy 
removal  and  quick  replacement  after  inspection,  the  time  of  the 
inspector  can  be  reduced  to  the  minimum.  Through  the  use  of 


120 


THE  CONTROL  OF  QUALITY 


trucks  such  as  shown  by  the  illustrations  in  this  article,  counting  is 
unnecessary,  as  the  inspector  knows  from  the  Production  Order 
card  the  total  number  the  truck  or  box  should  contain,  and  only 


Figure  22.     An  "A"  Frame  Wood  Truck  for  Connecting  Rods 

The  rough  forging  is  placed  in  the  truck  in  the  raw-stock  room  and  the  finished 

rod  is  taken  off  in  the  finished-stock  room. 


has  to  subtract  the  missing  pieces  from  this  total.     This  counting 
of  the  missing  parts  can  be  done  at  a  glance. 

The  finished  parts  stockroom  is  also  benefited  in  several  ways  by 
the  special  trucks,  as  the  counting  of  material  as  received  is  ex- 
pedited and  a  visual  inspection  can  be  made  in  a  short  time.  If  the 


CENTRAL  INSPECTION 


121 


122  THE  CONTROL  OF  QUALITY 

material  is  to  be  stocked  in  bins,  the  truck  can  be  pushed  to  the  loca- 
tion and  emptied  as  desired.  Frequently  the  material  is  to  be  used 
in  other  assembly  operations,  and  if  allowed  to  remain  on  the  truck 
it  can  be  sent  at  once  without  further  work  to  the  assembly  depart- 
ment. I  n  preparing  material  for  group  assemblies  the  special  trucks 
can  be  loaded  in  the  finished  parts  stockroom  with  speed  and  the 
assurance  that  no  damage  will  result  while  in  transit,  and  that  the 
count  is  correct  as  to  the  number  of  pieces  sent  out. 

Operators  working  on  a  piecework  basis  will  not  try  to  claim 
pay  for  the  full  amount  of  the  order  if  some  parts  are  missing,  as  the 
evidence  of  such  missing  pieces  is  open  to  the  time  clerk  and  the 
foreman  at  a  glance.  In  the  matter  of  placing  the  responsibility 
for  scrap  it  is  very  easy  for  a  foreman  to  check  the  actual  amount  of 
material  coming  into  his  department  in  order  to  be  sure  that  the 
Production  Order  shows  the  amount  scrapped  on  previous  opera- 
tions. This  is  a  factor  frequently  overlooked  in  the  design  of 
equipment  to  move  material. 


The  Two-Bin  System  Extended 

Consider  an  application  in  the  shop  of  what  Dr.  Fred- 
erick W.  Taylor,  I  believe,  called  the  "two-bin"  system. 
Its  application  in  modern  storehouses  is  generally  known. 
For  each  article  stored  and  issued  with  any  frequency,  two 
storage  spaces  are  provided  instead  of  one,  as  usual  under 
the  older  system.  Or  perhaps  it  would  be  more  accurate  to 
say  that  the  storage  bin  or  other  space  is  divided  into  two 
parts,  A  and  B.  Issues  of  stock  are  made  from  A  until  it 
is  empty.  Meanwhile  new  stock  is  accumulated  in  B,  as 
it  is  received  in  the  storehouse.  As  soon  as  A  is  empty 
the  storekeeper  begins  to  issue  from  5,  and  to  accumulate 
new  stock  in  A,  and  so  on,  alternating  the  issuing  bin, 
which  is  indicated  by  a  tag  or  movable  indicator.  In 
this  way  no  old  stock  is  permitted  to  lie  in  the  bottom  of 
the  bin,  as  is  almost  certain  to  be  the  case  when  new  stock 
is  piled  in  on  top  of  old  stock  in  the  single-bin  system  of 
storehousing. 


CENTRAL  INSPECTION  123 

Systematic  Layout  for  Material  in  Process 

A  continuous  flow  of  work  through  the  shop  indicates  the 
desirability,  and  perhaps  the  necessity,  of  laying  out  the 
storage  spaces,  for  banks  of  material  in  process,  on  the  two- 
bin  system.  For  example,  with  banks  carrying  a  day's 
supply  the  two-bin  scheme  can  be  worked  by  issuing  from 
one  end  of  the  pile  today,  from  the  other  end  tomorrow,  and 
so  on,  alternating  each  day  or  each  shift  if  the  flow  is  rapid. 
Under  a  system  of  central  inspection  the  storage  spaces  for 
material  should  be  systematically  arranged  with  this  object 
in  view.  Needless  to  say,  control  of  the  flow  is  much  sim- 
plified under  such  an  application  of  central  inspection. 

As  a  preliminary  step  to  taking  up  the  arrangement  of 
the  shop  under  central  inspection,  attention  is  invited  to  the 
following  diagram  (Figure  24),  which  indicates  the  theo- 
retical line  of  flow  of  work : 

First  Operation  Second  Operation 


Figure  24 

So  represents  the  stores  of  raw  material  for  the  part  in 
question,  which  is  daily  or  hourly  issued  to  replenish  the 
material  waiting  for  the  first  manufacturing  operation  at 
the  process  storage  point  Si — preferably  arranged  in  two 
parts,  or  piles  of  work,  on  the  two-bin  system,  and  in  self- 
counting  tote  boxes.  From  Si  the  work  is  issued  as  needed, 
one  box  at  a  time,  to  the  operator  at  the  production  point, 
PI.  The  production  point  in  question  may  be  one  machine 
or  a  group  of  machines,  under  one  or  several  operators,  or 
it  may  be  a  bench  job  or  some  special  test.  After  the  oper- 
ator at  PI  finishes  the  box  of  work,  it  is  removed  to  the  in- 
spection point  1 1,  where  it  may  be  inspected  in  whole  or  in 
part  (in  whole  only  if  100  per  cent  inspection  is  required)  or 
perhaps  merely  counted  by  the  inspector.  After  the  inspec- 


124  THE  CONTROL  OF  QUALITY 

tion,  the  tray  of  work  is  moved  to  S2,  the  storage  point  for 
work  waiting  for  the  time  being  for  the  next  manufacturing 
operation.  When  certain  parts  are  rejected  and  a  "broken" 
box  results,  the  box  should  be  filled  up  from  the  next  box  of 
parts  or  from  a  small  stock  kept  for  that  purpose  in  the  in- 
spection room,  so  that  only  full  boxes  are  issued  from  S2 
to  P2,  and  so  on. 

Layout  of  Central  Inspection  Crib 

In  centralizing  the  inspection  into  a  central  inspection 
system,  we  bring  together  in  a  central  place  and  in  accord- 
ance with  some  convenient  arrangement  all  of  the  storage 
points  (or  banks  of  material  in  flow)  and  the  inspection 
points,  leaving  in  the  shop  proper  nothing  but  the  produc- 
tion points,  together  with  such  work  as  is  actually  being  put 
through  the  machines  at  the  production  points  in  question. 
This  means,  when  the  system  is  carried  to  the  limit,  that 
after  working  hours  all  work  in  flow  will  be  in  the  central 
inspection  spaces,  and  therefore  there  will  be  no  work  at 
the  machines,  which  condition  insures  a  complete  count 
of  each  day's  work  and  tends  to  prevent  trouble  of  various 
kinds,  including  the  temptation  to  steal  parts. 

In  concentrating  the  storage  and  inspection  points  at 
some  central  place  or  places  in  the  shop,  the  greatest  econ- 
omy will  be  secured  by  a  shop  arrangement  that  reduces  the 
PI  Po  p\  distances  between  any  two 

"  /  ~  consecutive  points  in  the  line 

11  *2  l3/etc<  of  flow,  Slt  Pi,  /i,  52,  P2,  72, 

s,  sa  S3)  S3,  P3,  /s,  etc.,  as  much  as 

possible.      For    example,    a 
12/  good  arrangement  would  be 

1 10  In  Ii2)etc-  that  shown  in  Figure  25. 

PW~       ~^n~      "  PM)  The  dotted  line  indicates 

Figure  25  the  separation  between  the 


CENTRAL  INSPECTION  125 

shop  proper,  with  its  production  points  PI,  P2,  etc.,  and  the 
central  inspection  space  or  crib  containing  the  correspond- 
ing storage  points  and  inspection  points. 

As  a  matter  of  fact,  the  diagrammatic  arrangement  just 
shown  gives  an  erroneous  conception  of  the  quantitative 
space  assignment  required,  because  /  and  S  ordinarily  re- 
quire much  less  space  than  P.  Frequently  /  will  represent 
only  a  counting  of  the  work,  without  inspection.  It  is  in- 
teresting to  note,  however,  that  a  uniform  distribution  of 
work  in  flow  (especially  when  standard  sized  tote  boxes  are 
stacked  in  piles)  carries  with  it  the  condition  that  the  spaces 
provided  for  all  storage  points  be  the  same  in  size.  The 
same  thing  can  be  expressed  in  much  shorter  form  by  say- 
ing that  Si  =  S2  =  S3,  etc.,  which,  incidentally,  is  a  nice  ex- 
ample of  the  saving  in  time  from  the  use  of  symbols. 

It  is  very  likely,  therefore,  that  the  following  diagram 
(Figure  26)  more  accurately  shows  the  relative  size  of  the 
space  assignments  for  such  an  arrangement: 

PI  P*  P,    etc. 


la 

lao                I2 

la: 

Is 

I 

s, 

SIQ                S2 

Su 

S3 

s 

)etc. 


PIO  PH  P12  etc. 

Figure  26 

Construction  of  Central  Inspection  Cribs 

It  does  not  follow,  by  any  means,  that  the  collection  of 
the  points  5"  and  /  in  a  central  inspection  space  requires 
that  this  space  be  separated  from  the  rest  of  the  shop  by 
partitions.  That  is  a  question  which  must  be  settled  by  the 
class  of  work  involved  and  by  the  conditions  attending  its 


126 


THE  CONTROL  OF  QUALITY 


Figure  27.     Transporting  Rack  for  Rifles — Remington  Armory,  Bridgeport 

Note  especially  the  construction  of  the  type  inspection  crib  in  the  background. 


CENTRAL  INSPECTION 


127 


manufacture.  In  many  instances  it  is  only  essential  that 
the  central  inspection  space  be  indicated  by  lines  painted  on 
the  floor,  or  by  some  other  means  of  showing  the  physical 
separation  of  the  principal  functions  that  has  been  made. 
A  light  railing  may  suffice. 

When  the  use  of  a  partition  is  indicated  by  the  local  con- 
ditions, one  of  the  best  plans  is  to  erect  a  light  framework, 
supporting  woven  wire  to  a  height  of  6  or  8  feet.  Chicken 


Braces- 


Support_ 


luppo 
2'k4 


Closed  in  by  sheets  of 
fiber  board  where 
.female  inspector  are 
employed. 


-Woven  wire,  inside  of  supports 


Gage  &  inspection 

«-  instruction  cards, 

sample  parts,  etc. 


r\\ 


•J 


Figure  28.     Type  Section  of  Central  Inspection  Crib 

wire  will  do.  (See  Figure  28  showing  a  type  section,  of  a 
central  inspection  crib.) 

The  woven  wire  is  preferably  put  up  inside  the  line  of 
supports.  This  arrangement  avoids  lost  space  and  objec- 
tionable holes  behind  the  inspection  benches  on  the  one 
side  of  the  central  inspection  crib,  and  permits  more  or- 
derly storage  of  work  in  process  banks  on  the  other  side  of 
the  crib. 

When  partitions  are  used,  it  becomes  necessary,  of 
course,  to  provide  openings  through  which  work  may  be 
passed.  If  the  work  is  bulky  and  each  storage  unit  of  parts 


128  THE  CONTROL  OF  QUALITY 

is  carried  on  wheels,  for  example,  the  opening  should  ex- 
tend upward  from  the  floor  to  a  height  just  sufficient  to  per- 
mit the  comfortable  entrance  of  the  carrying  device.  Smaller 
parts,  that  are  handled  in  tote  boxes  or  trays,  usually  require 
only  a  passing  window  with  a  shelf.  These  windows  should 
be  spaced  close  enough  together  to  avoid  too  long  distances 
from  machines  to  windows.  At  the  same  time  they  should 
be  spaced  far  enough  apart  to  avoid  interference  with  the 
inspection  benches.  It  is  not  good  practice  in  this  case,  nor 
is  it  ordinarily  necessary,  to  have  the  machine  operator  de- 
liver his  work  directly  to  the  inspector  who  is  to  inspect  and 
count  it.  There  is  far  less  chance  of  connivance  between 
inspector  and  workman,  together  with  less  interference  with 
the  actual  work  of  inspecting  and  counting,  if  the  work  is 
issued  and  received  by  the  working  foreman  in  the  inspec- 
tion crib,  or  perhaps  by  an  assistant.  Women  inspectors, 
for  example,  may  be  employed  on  quite  heavy  work  if  they 
are  relieved  from  having  to  lift  tote  boxes  full  of  parts. 
When  the  flow  is  rapid,  a  worker  of  the  common  labor  class 
will  be  fully  employed  in  moving  tote  boxes  to  and  from  the 
issuing  windows  and  the  storage  points. 

Referring  again  to  the  typical  diagram,  the  introduction 
of  partitions  with  passing  windows,  or  doors,  brings  about 
the  arrangement  shown  in  Figure  29. 


p  p   p 

Figure  2).     Floor  Plan  of  Central  Inspection  Crib 


CENTRAL  INSPECTION 


129 


An  Adaptation  to  Rough  Work 

It  is  now  proposed  to  show  the  application  of  central 
inspection  in  two  cases,  illustrating  the  extreme  conditions 
that  are  likely  to  be  encountered.  The  first  example  is  that 
of  a  shop  making  a  relatively  small  but  bulky  article,  such 
as  heavy  canvas  bags.  The  processing  involves  cutting  the 
canvas  and  folding  once,  sewing  the  side  seams,  binding  over 


"i  r 

i  i 

i  i 

i  i 


i  i 
i  i 


i  i 

.J      L. 


Elevators 

Stairway, 

fashroomi , 

etc. 


Figure  30.     Floor  Plan  of  Canvas  Shop 

and  sewing  the  top  seam,  inserting  a  row  of  brass  grommets 
above  the  latter,  and  finally  passing  a  gathering  cord  through 
the  grommets  and  attaching  a  fastening  device  to  the  cord. 
The  work  is  counted  automatically  by  the  issue  of  lots  of 
100  pieces  (on  lifting  platforms)  from  a  central  inspection 
space.  Inspection,. however,  is  by  sampling  at  the  machines, 
except  after  completion  of  the  bags,  at  which  stage  there  is 
a  100  per  cent  final  inspection.  In  this  instance  it  is  less 
expensive  to  allow  an  occasional  bad  piece  of  work  to  slip 
through  than  to  provide  a  closer  inspection. 


130  THE  CONTROL  OF  QUALITY 

Each  shop  was  located  in  a  room  approximately  100  feet 
square,  with  machines,  work  benches,  and  work  in  process 
scattered  throughout,  but  arranged  in  a  general  way  in  the 
order  of  operation  sequence.  The  rearrangement  is  indi- 
cated in  Figure  30. 

One  end  of  the  shop  was  darkened  by  elevators,  stair- 
ways, washrooms,  and  similar  enclosures — a  condition  fixed 
by  the  building.  The  dark  space  in  the  middle  of  the  shop 
(indicated  by  I-S)  was  cleared  of  machines,  which  were 
moved  out  to  the  light  (P,  P,  P).  The  center  aisle  lines 
were  closed,  and  the  new  aisle  lines  painted  on  the  floor  as 
indicated  by  the  dotted  lines.  The  new  aisles  were  kept 
clear  at  all  times.  At  each  machine,  two  spaces  (or  platforms 
for  lifting  trucks)  were  located  to  provide  one  place  for  the 
lot  of  pieces  ready  for  the  machine  and  another  place  for 
work  just  passed  through  the  machine. 

The  Resulting  House  Cleaning 

The  central  inspection  space  I-S  was  not  enclosed,  but 
its  boundaries  were  clearly  indicated  by  the  arrangement  of 
benches  and  of  work  in  the  storage  banks.  As  a  part  of  the 
process  of  rearranging  this  shop,  the  foreman  was  instructed 
to  clean  house,  and  in  doing  so  to  be  guided  by  the  rule  that 
everything  not  needed  and  used  in  the  work  must  be  dis- 
carded. After  he  was  through,  a  wagon-load  of  junk  was 
removed,  in  the  form  of  unnecessary  shop  furniture,  old 
signs,  ancient  records,  and  what-not,  extending  even  to 
bench  drawers  that  served  no  useful  purpose.  The  subse- 
quent application  of  a  coat  of  white  paint,  and  the  introduc- 
tion of  the  more  orderly  and  systematic  control  of  work  in 
flow,  created  an  obviously  different  working  atmosphere. 
Incidentally  the  scrap  value  of  the  stuff  removed  paid  for 
the  direct  cost  of  the  clean-up. 

This  simple  case  has  been  cited  for  the  reason  that  it  is 


CENTRAL  INSPECTION  131 

typical  of  a  large  class  of  work  (often  relatively  rough  work) , 
to  which  the  general  principles  and  methods  of  central  in- 
spection can  be  applied  with  advantage. 

An  Adaptation  to  Close  Work  in  Metal 

Let  us  now  proceed  a  very  long  way  up  the  scale  of  appli- 
cation of  central  inspection,  until  we  reach  the  other  limit. 
In  this  case  central  inspection  is  to  be  applied  to  a  shop  mak- 
ing in  quantity,  high-grade  steel  parts  of  relatively  small 
size — the  machining  is  intricate,  the  limits  are  very  close, 
the  parts  are  strictly  interchangeable,  limit  gages  are  in  use, 
and  the  finish  must  be  excellent.  In  short,  the  work  is  diffi- 
cult, comparatively  costly,  and  the  standard  of  quality  is 
almost  high  enough  to  approximate  to  that  required  for  the 
very  tools  used  in  making  the  parts.  Evidently,  there  will 
be  need  for  close  inspection  after  all  important  operations, 
sampling  for  practically  all  operations,  and  100  per  cent 
inspection  of  all  finished  parts.  Since  such  work  is  ordina- 
rily found  in  large  factories,  we  may  assume  as  well  that  the 
shop  in  question  is  only  one  of  several  such  shops  and  that 
it  handles  the  machining  of  but  one  of  the  parts — or  at  most 
only  a  few  of  them — that  are  to  become  components  of  a 
complex  mechanism. 

In  a  case  of  this  kind,  central  inspection  is  a  machine 
with  a  vitally  important  service  to  perform.  Like  any  fine 
machine  it  should  be  designed  with  the  greatest  attention 
to  details.  It  may  have  to  be  intricate,  yet  the  design 
should  follow  the  simplest  and  most  economical  line  for 
accomplishing  the  desired  result.  Such  an  adaptation  of 
central  inspection  is  the  most  highly  specialized  form  of 
inspection,  and  as  such  is  the  ideal  instrument  both  for  use 
in  controlling  quality  and  for  insuring  a  uniform  flow  of 
work. 

The  usual  type  of  factory  floor  for  such  work  is  from  60 


132 


THE  CONTROL  OF  QUALITY 


to  80  feet  wide  (a  greater  width  interferes  with  lighting) ; 
some  250  feet  or  more  long;  and  built  with  sides  con- 
structed of  steel  and  glass  sash  extending  from  the  ceiling  to 
within  about  3  feet  of  the  floor.  While  the  glass  siding  is 
sometimes  carried  down  to  the  floor,  such  construction  is  not 
desirable  for  work  of  this  kind,  as  the  light  shining  up  from 
below  the  machines  is  trying  on  the  eyes  and  therefore  of 
deleterious  effect  on  the  work.  There  will  be  no  really  dark 
spaces  in  the  shop,  but  the  light  may  not  be  so  good  at  the 
exit  and  entrance,  nor  at  one  of  the  corners  at  each  end  of 


Figure  31.     Typical  Modern  Shop  Floor  Plan 

the  shop,  if  enclosed  fire  towers  are  built  in  at  these  points. 
The  state  laws  require  that  clear  passageways  be  preserved 
from  end  to  end  of  the  shop,  for  use  in  case  of  fire  or  panic. 
A  frequent  arrangement  of  a  typical  shop  floor  of  this  sort, 
as  shown  in  Figure  31,  provides  for  clear  aisles  at  a,  a,  a,  a, 
between  the  rows  of  columns. 

Aisle  Arrangement 

The  aisles  bb,  connecting  shop  to  shop  may  be  found  at 
the  middle  or  end  of  the  room,  and  since  they  are  used  for 
intershop  traffic,  must  always  be  kept  open. 

Whether  there  are  columns  or  not,  it  is  usual  to  provide 
for  a  central  aisle,  which  is  kept  clear  at  all  times  (at  least  in 
theory).  Concurrently,  it  is  necessary  to  have  other  aisles 


CENTRAL  INSPECTION  133 

paralleling  the  main  aisles,  but  out  among  the  machines,  to 
permit  of  the  passage  of  men  and  material  to  the  machines. 
These  aisles  are  not  so  well  defined,  unless  the  machine  ar- 
rangement is  a  simple  and  orderly  one.  It  should  be  noted, 
however,  that  the  aisles  in  question  usually  can  be  regulated 
into  clear  and  fairly  well-defined  passageways,  thus  per- 
mitting the  use  of  the  former  middle  aisle  for  central  inspec- 
tion. In  many  cases,  especially  when  combined  with  central 
storage  of  work  in  process,  this  arrangement  will  result  in 


6 

/A 

C 

< 

\   [ 

1 
J 

\  B 

\ 

D 

d 

Figure  32.     Modern  Shop  Floor  Arranged  for  Central  Inspection 

an  actual  economy  of  floor  space,  due  chiefly  to  more  effi- 
cient use  of  the  space  otherwise  taken  up  by  work  in  process. 
There  is  developed  in  this  way  the  arrangement  shown  in 
Figure  32. 

The  necessities  of  transportation  and  emergency  exit  are 
met,  under  these  circumstances,  in  two  ways : 

I.  At  least  one  fairly  well-defined  passageway  is  pro- 
vided among  the  machines  at  each  side  of  the  shop,  along  the 
lines  abc  and  ade.  There  must  be  a  passageway  among  the 
machines;  and  since  the  machines  are  in  fixed  locations,  the 
principal  cause  of  blocked  passageways  is  eliminated  when 
the  material  at  each  machine  is  limited  to  one  standard- 
size  lot  of  parts. 


134  THE  CONTROL  OF  QUALITY 

2.  These  aisles  are  supplemented  by  providing  double- 
swing  doors  (if  any  are  required)  at  the  ends  (AB  and  CD) 
of  the  enclosed  inspection  space  A  BCD.  The  inspection 
benches  and  material  in  process  along  the  sides  A  C  and  BD 
decrease  the  effective  width  of  the  former  central  aisle,  but 
not  so  much  as  to  eliminate  the  passageway.  The  side 
aisles  are  therefore  supplemented  by  a  more  restricted  cen- 
ter aisle,  and,  all  in  all,  ample  gangway  is  secured. 

There  are  many  other  arrangements,  of  course,  in  which 
a  shop  can  be  laid  out  to  provide  for  central  inspection,  but 
the  scheme  just  outlined,  while  of  admitted  uniqueness,  has 
much  to  commend  it  in  many  cases.  It  provides  a  central 
place  from  which  to  distribute  work,  economizes  the  floor 
space  of  the  whole  shop,  and  can  be  used  in  adapting  central 
inspection  to  many  shops  not  originally  arranged  for  this 
system  of  control.  Any  such  location  of  inspection  cribs 
carries  with  it  a  positive  requirement  for  artificial  lighting  of 
the  inspection  benches,  but  this  is  not  a  serious  objection 
because  the  more  uniform  light  of  good  artificial  illumination 
has  much  to  commend  it  for  inspection  purposes. 

Advantages  of  Several  Centralized  Inspection  Spaces 

Whether  this  or  some  other  plan  is  adopted  for  the  loca- 
tion of  the  central  inspection  cribs,  it  is  well  to  observe  that 
central  inspection  does  not  imply  one  inspection  room  only, 
nor  even  one  room  only  in  each  shop.  On  the  contrary,  the 
more  efficient  arrangement  in  a  large  shop  is  to  place  the 
cribs  at  the  locations  where  they  give  the  maximum  of  serv- 
ice with  the  least  interference  to  traffic.  The  governing 
conditions  should  be  that  each  inspection  crib  be  centrally 
placed  with  reference  to  the  machines  it  is  to  serve,  and  that 
it  be  large  enough  to  store  its  proper  quota  of  work  in 
process. 

The  least  interference  with  traffic  is  secured  when  the 


CENTRAL  INSPECTION 


135 


crib  is  parallel  to  and  near  the  normal  line  of  flow  of  work. 
It  will  be  found  that  there  is  much  lost  space  in  the  ordinary 
shop  arrangement  which  can  be  made  available  if  the  shop 
layout  is  carefully  planned  with  reference  to  the  space 
occupied  by  work  in  process  as  well  as  that  taken  up  by 
machinery.  Thus,  if  there  is  insufficient  room  for  all  of  the 
inspection  work  in  the  shop  itself,  the  next  logical  place  to 
utilize  is  some  space  on  the  side  of  the  passage  from  shop  to 
shop.  It  is  quite  usual  to  find  unused  space  going  to  waste 
in  these  locations.  In  such  case  it  is  clear  that  this  space 
should  be  utilized  for  the  inspection  work  that  can  best  be 
spared  from  the  neighborhood  of  the  machines,  i.e.,  the  final 
inspection  of  finished  parts,  and  the  salvage  or  reinspection 
of  rejected  work. 

Standard  Arrangement  Desirable 

Reference  already  has  been  made  to  the  fact  that  each 
inspection  crib  should  be  designed  with  great  care  as  to  the 
details,  but,  naturally,  each  crib  should  be  laid  out  in  ac- 


w 

L^ 

w 

.                         T 

F 

<                  1                    > 

—  =  > 

n       n       a 

a     a     a     a 

a       a       a 

( 

fe_S,—  > 

I 

r   r      i    -  } 

a  i  6 

U  s  J 

i     1            1        : 

1  l 

i  i 

w~ 

W 

Figure  33.     Type  Floor  Plan  of  Central  Inspection  Crib 

cordance  with  a  general  unified  plan  for  all  of  them.  To 
illustrate,  the  outline  shown  in  Figure  33  may  be  assumed 
to  be  that  of  a  central  inspection  crib  which  is  typical  for  a 
given  factory. 

The  size  of  the  crib  will  be  determined  in  a  general  way 


136  THE  CONTROL  OF  QUALITY 

by  the  amount  of  space  required  for  storage  of  work  in  proc- 
ess, for  the  reason  that  if  this  space  is  provided  on  one  side 
of  the  crib  there  is  pretty  sure  to  be  room  enough  for  the 
inspection  benches  on  the  other  side.  The  passing  windows 
w,  w, —  will  be  placed  at  fairly  uniform  intervals,  but  this 
should  not  be  a  fixed  rule,  as  the  most  convenient  locations, 
with  reference  to  the  number  of  machines  to  be  served, 
should  be  selected. 

As  the  normal  work  bench  with  wooden  top,  back  rail, 
foot  rail,  and  metal  frame  support  is  satisfactory  for  the  pur- 
pose, a  number  of  them  should  be  placed  at  i,  i—  and  shop 
stools  provided.  Reasonable  bodily  comfort  is  a  great 
relief  to  the  confining  tedium  of  bench  inspection.  Bench 
drawers  are  not  desirable  in  most  instances.  If  it  is  neces- 
sary to  provide  against  the  chance  of  gages  being  tampered 
with  outside  of  working  hours,  a  cupboard,  with  a  lock,  may 
be  provided. 

On  the  side  of  the  crib  opposite  the  inspection  benches, 
the  space  should  be  marked  off  for  storage  of  work  in  flow. 
If  the  two-bin  principle  is  followed,  each  unit  storage  space 
should  have  two  sections,  as  Si  (a)  and  (b).  There  is,  of 
course,  a  natural  limit  in  the  height  to  which  any  kind  of  tote 
box  can  be  piled  with  safety  and  this  fact  should  be  con- 
sidered in  laying  out  the  storage  point.  Furthermore,  the 
height  that  corresponds  with  the  number  of  boxes  of  work 
required  in  each  bank  to  maintain  the  flow  should  be  in- 
dicated on  the  side  of  the  crib.  With  these  refinements  in 
use,  each  storage  point  will  be  shown  by  a  card  or  other 
mark  on  the  side  of  the  crib,  as  shown  in  Figure  34. 

A  pointer  may  be  used  to  indicate  the  issuing  pile,  but  is 
not  necessary  if  the  issuing  and  receiving  sections  are  re- 
versed automatically  at  given  times. 

The  inspection  benches  should  be  marked  off,  or  the 
inspection  points  indicated  by  labels  showing  the  operation 


CENTRAL  INSPECTION 


137 


symbols  on  the  side  of  the  crib  above  the  benches.  It  may 
be  found  very  useful  to  supply  a  gage  instruction  card, 
telling  in  detail  how  the  gages  are  to  be  applied,  and  setting 
forth  the  special  points  to  be  looked  after.  It  is  often  de- 
sirable to  furnish  sample  parts,  which  should  be  tied  to  the 
side  of  the  crib  over  the  bench,  to  prevent  their  becoming 
mixed  with  the  regular  work.  (See  Figure  12,  page  71.) 

Assuming  a  di- 
rection of  flow 
from  left  to  right 
in  Figure  33,  the 
inspection  points 
will  be  arranged  in 
this  order,  a  sepa- 
rate bench  being 
provided  at  F  for 
the  use  of  the 
crib  boss  or  work- 
ing foreman  of 
the  crib.  Among 
other  purposes, 
this  bench  will 
serve  as  an  issuing 
point  for  working 
gages,  which  is  an  essential  feature  of  quality  control,  as 
will  be  noted  later  under  the  subject  of  gage-checking. 

Summary  of  Advantages 

The  advantages  of  providing,  within  the  producing  shop, 
a  central  inspection  crib  combined  with  a  storehouse  for 
parts  in  process,  may  be  summarized  as  follows : 

i.  The  work  can  be  stored  in  self -counting  trays.  A 
workman  will  come  to  the  issuing  window  and  obtain  a  box 
of  parts,  which  he  will  machine  and  return.  The  inspector 


Figure  34.     Type  Arrangement  of  Material  Storage 
Point  in  Central  Inspection  Crib 


138  THE  CONTROL  OF  QUALITY 

will  find  that  some  are  good  and  some  bad,  and  the  work- 
man will  be  credited  accordingly.  He  will  be  paid  for  what 
he  does — and  for  no  more  nor  less.  This  will  insure,  among 
other  things,  the  collection  of  accurate  data  as  to  what  is 
going  on  in  the  way  of  production  and  will  tend  to  do  away 
with  losses  from  stolen,  destroyed,  or  lost  parts. 

2.  There  will  be  nothing  at  the  machines  outside  of 
working  hours,  and  nothing  at  each  machine  but  a  box  of 
parts  at  any  time  during  working  hours — result,  a  clean 
shop,  and  a  clear  one. 

3.  The  systematic  arrangement  of  all  parts  in  flow  makes 
it  possible  to  check  up  the  flow  by  quickly  visualizing  its 
condition,  i.e.,  it  is  possible  to  plan  with  the  material  itself 
rather  than  with  figures  alone.     A  walk  through  the  crib 
tells  the  story. 

4.  The  control  of  quality  is  more  certain,  as  the  work  of 
the  inspectors  can  be  supervised  to  greater  advantage  and 
the  custody  of  work  in  process  is  well  centralized.     The  in- 
formation necessary  for  inspection  can  be  so  arranged  in 
useful  form  by  providing  each  inspection  point  with  stand- 
ard samples,  gaging  lists  giving  the  symbol  of  the  gage  to 
be  applied  and  the  percentage  of  inspection,  gage  instruc- 
tions, etc.     All  gages  can  be  issued  and  controlled  from  this 
point. 

5.  The  routing  and  flow  of  work  is  under  sure  control. 


CHAPTER  IX 

THE  ORGANIZATION  OF  THE  INSPECTION 
DEPARTMENT 

Designing  the  Instrument  for  Controlling  Quality 

Before  plunging  into  the  particulars  of  a  subject  like 
"  organization,"  a  term  which  is  often  confused  with  the  re- 
lated terms  "administration"  and  "management,"  it  would 
seem  to  be  worth  while  to  make  sure  at  the  outset  of  what 
we  mean  by  "organization."  In  order  to  separate  out  the 
idea,  let  us  first  think  of  the  inspection  department  as  a 
machine  or  an  instrument  for  use  in  the  control  of  quality, 
together  with  certain  secondary  duties  to  be  combined 
therewith  as  a  matter  of  economy.  The  organization  of  the 
inspection  department  may  be  considered  as  comparable  to 
the  design  of  the  machine,  and  the  administration  or  man- 
agement of  the  inspection  department  as  comparable  to  the 
operation  of  the  machine  thus  designed.  In  accordance 
with  the  foregoing  analysis,  questions  affecting  the  manage- 
ment of  the  inspection  department  will  be  discussed  in  the 
succeeding  chapter: 

The  Development  of  Organization 

The  process  by  which  organization  develops  may  be 
analyzed  into  three  steps: 

1.  There  is  a  union  or  grouping  of  individuals  for  a  com- 
mon purpose.     From  this  fact,  arises  a  necessity  for  organ- 
izing. 

2.  The  work  necessary  to  accomplish  the  purpose  is 
divided  and  distributed  so  that  each  group  of  individuals 
performs  the  work  allotted  to  it  with  undivided  authority 

139 


140  THE  CONTROL  OF  QUALITY 

and  individual  responsibility.  This  division  of  duties  tends 
to  become  more  complex  as  the  number  of  persons  involved 
increases  or  as  the  scope  of  the  work  broadens. 

3.  The  interdependence  resulting  from  the  preceding 
steps  demands  a  co-ordinating  of  the  work  of  the  separate 
parts  or  groups,  in  order  to  secure  co-operative  action,  and 
thus  to  weld  all  groups  into  one  coherent  whole  so  that  all 
work  harmoniously  toward  the  common  objective. 

Organization  begins  with  the  first  of  these  stages,  it  is 
developed  by  the  second,  and  is  completed  and  perfected 
by  the  last.  The  higher  the  type  of  organization,  the  more 
intricate  is  the  distribution  and  division  of  labor;  and  this 
fact,  in  turn,  calls  for  better  co-ordination,  together  with 
closer  and  stronger  co-operation. 

In  the  light  of  these  general  observations  we  may  pro- 
ceed to  design  an  organization  for  the  inspection  department. 
As  we  are  designing  with  men  as  our  material  the  design 
must  conform  to  the  capabilities  of  the  men  that  are  avail- 
able; furthermore  it  must  be  suited  to  the  conditions  im- 
posed by  the  character  of  the  work  to  be  performed.  The 
discussion  that  follows  applies,  as  will  be  noted,  to  the  or- 
ganization of  an  inspection  department  for  a  large  factory 
doing  high-grade  interchangeable  manufacturing,  but  the 
same  principles  apply  in  simpler  cases,  and  the  organization 
may  be  readily  and  suitably  simplified  for  such  situations. 

The  Chief  Inspector 

It  is  almost  begging  the  question  to  say  that  if  the  right 
man  is  at  the  head  of  the  inspection  department,  there  need 
be  no  worries  about  the  organization  and  management  of 
that  department.  But  what  type  of  man  is  called  for?  The 
position  is  one  of  trust,  hence  character  is  an  indispensable. 
Good  judgment  is  requisite,  not  only  the  judgment  that 
flows  from  "mechanical  sense"  and  skilled  ability  as  an 


ORGANIZATION  OF  INSPECTION  DEPARTMENT          141 

engineer,  but  also  plain  "horse  sense."  In  addition  the 
man  must  be  an  executive  of  no  mean  ability. 

Many  persons  have  been  so  accustomed  to  regarding  in- 
spection as  one  of  the  secondary  features  of  manufacturing, 
that  they  fail  to  realize  what  complex  and  extensive  organi- 
zations have  been  evolved  for  the  inspection  departments  of 
large  factories.  It  is  by  no  means  an  uncommon  thing 
nowadays  to  find  an  inspector  for  every  10  to  20  workmen, 
and  the  proportion  may  be  much  higher.  In  the  Wahl 
Company  of  Chicago,  which  manufactures,  among  other 
things,  the  ubiquitous  Eversharp  pencil,  the  proportion  of 
inspectors  is  i  to  8.6  workers.1  In  the  S.  K.  F.  Ball  Bearing 
Company's  plant  at  Hartford,  where  every  operation  is  100 
per  cent  inspection,  27  per  cent  of  all  the  productive  workers 
are  employed  in  the  inspection  department.2  Under  diffi- 
cult war  conditions,  the  inspection  department  of  one  of  the 
munition  plants  reached  a  total  figure  of  2,200  employees, 
and  possibly  there  were  larger  inspection  forces  in  other 
plants. 

Even  under  normal  conditions,  it  will  be  recognized 
from  the  above  figures,  the  head  of  the  inspection  depart- 
ment has  an  executive  job  of  no  mean  size.  The  duty  is 
very  greatly  enlarged  and  complicated,  moreover,  by  reason 
of  the  fact  that  the  inspection  department  is  not  concen- 
trated into  one  definitely  bounded  shop,  like  the  various 
production  departments.  On  the  contrary,  its  work  reaches 
into  nearly  every  part  of  the  factory,  and  in  consequence  its 
personnel  is  widely  scattered.  The  character  of  the  work 
is  at  least  as  diversified  as  the  processing,  which  fact  still 
further  complicates  the  problem;  for  the  inspection  force 
will  have  one  group  of  workers  in  the  wood-working  depart- 
ment, for  example,  while  a  thousand  yards  away  it  will  have 

1  Furnished  through  the  courtesy  of  C.  A.  Frary,  General  Manager. 

2  Courtesy  of  R.  F.  Runge,  General  Factory  Manager  of  S.  K.  F.  Industries,  Inc. 


142  THE  CONTROL  OF  QUALITY 

another  group  engaged  in  the  inspection  of  metal  parts  made 
to  standards  of  accuracy  so  precise  as  often  to  split  thou- 
sandths of  an  inch.  Therefore  the  chief  inspector  should  be 
generally  familiar  with  all  shop  processes  rather  than  a 
specialist  in  a  limited  number  of  them. 

Duties  of  the  Inspection  Department 

Concurrently  with  selecting  a  man  to  take  charge  of  the 
inspection  department,  there  arises  the  problem  of  outlining 
what  this  department  is  to  include.  Conversely,  the  amount 
of  work  that  it  is  expedient  to  include  will  determine  how 
big  a  man  should  be  selected  to  head  the  work.  The  two 
things  always  go  together,  and  the  resulting  solution  is 
usually  a  compromise.  Obviously,  the  duties  of  the  inspec- 
tion department  will  often  comprise  a  number  of  things 
that,  speaking  strictly,  are  not  inspection,  but  they  will  all 
be  related  to  inspection,  and  it  will  be  economical  and  wise 
to  include  them  with  inspection,  in  order  to  secure  a  more 
complete  control  of  quality. 

In  the  first  place,  there  will  be  the  separate  inspection 
forces  for  each  main  group  of  the  factory's  work,  as  in  the 
case  of  an  automobile  factory  making  .both  trucks  and  pas- 
senger cars.  Each  of  these  main  groups  will  be  subdivided 
into  an  inspection  force  for  each  shop,  or  smaller  factory 
unit,  including  the  assembling  shops. 

Work  Related  to  Process  Inspection 

In  addition  to  this  inherent  duty,  we  may  list  the  follow- 
ing: 

1.  Raw  material  inspection,  including  the  necessary 

laboratories,  chemical  and  physical. 

2.  Heat   treatment   inspection,    including  the   metal- 

lurgical and  metallographic  laboratories. 


ORGANIZATION  OF  INSPECTION  DEPARTMENT          143 

3.  Tool  inspection,  especially  if  the  factory  maintains  a 

tool-making  shop. 

4.  Gage-checking  and  the  verification  of  measuring 

standards,  all  in  close  co-operation  with  the 
chief  engineer. 

5.  General  supervision  of  the  assembling  department, 

in  some  instances,  where  inspection  in  this  depart- 
ment is  of  unusual  value  in  guiding  the  work  of  the 
parts-making  shops. 

6.  General  supervision  of  the  factory  salvage  depart- 

ment, when  it  is  specially  desirable  to  safeguard 
production  from  the  return  of  defective  work  into 
flow. 

The  inspection  of  machine  tools  and  similar  factory 
equipment,  as  well  as  of  the  buildings  and  their  appurte- 
nances, has  not  been  included  as  a  possible  assignment  of  the 
inspection  department,  for  the  evident  reason  that  the  in- 
spection and  maintenance  of  all  these  constitute  the  prin- 
cipal duty  of  the  works  engineer.  It  will  be  carried  out  by 
the  latter  with  due  regard  to  the  fact  that  every  department 
in  the  plant  will  be  "on  his  trail"  if  he  overlooks  anything 
that  requires  attention. 

The  general  test  for  deciding  whether  a  particular  branch 
of  factory  endeavor  should  be  included  in  the  inspection  de- 
partment is  simply  this — "Will  the  chief  inspector  handle 
it  to  the  better  advantage  of  the  entire  plant  or  not?"  The 
answer  depends,  of  course,  to  a  considerable  degree  upon 
who  and  what  the  chief  inspector  is. 

Undoubtedly  the  term  in  widest  use  to  designate  the 
head  of  the  inspection  department  is  that  of  "chief  inspec- 
tor." It  has  grown  up  in  much  the  same  way  as  the  title 
of  "chief  engineer,"  and  it  is  possibly  just  as  well  to  retain 
its  use,  although  there  are  many  organizations  in  which  the 


144  THE  CONTROL  OF  QUALITY 

strict  following  of  the  plan  used  in  the  general  factory  organ- 
ization chart  would  result  in  the  more  definite  title  of  "  man- 
ager of  inspection,"  or  possibly  that  of  " director  of  inspec- 
tion." The  matter  of  title,  however,  is  of  no  great  moment, 
for  the  greater  one's  experience  in  factory  work  the  less  will 
be  the  emphasis  placed  upon  titles.  But  there  is  a  matter  of 
marked  importance  which  should  not  be  overlooked  for  an 
instant  if  the  control  of  quality  is  to  be  assured — the  chief 
inspector  should  report  directly  to  the  highest  executive 
authority  in  the  management,  and  to  him  only. 

The  Line  Organization 

In  outlining  the  organization  under  the  chief  inspector's 
jurisdiction,  it  is  believed  that  the  best  result  will  be  obtained 
by  a  combination  of  line  and  staff,  as  in  the  case  of  the  gen- 
eral organization  of  the  factory  itself.  The  line  organization 
will  consist  of  the  usual  executive  heads  of  the  different 
groups  of  workers,  i.e.,  general  foremen-inspectors,  foremen- 
inspectors,  subforemen  or  crib-bosses,  and  so  on,  making  up 
the  " chain  of  command"  through  whom  instructions  will 
pass  from  the  chief  inspector  to  the  individual  inspectors  at 
the  bench. 

The  staff  of  the  chief  inspector  will  consist  of  a  few 
carefully  selected  specialists  who  have  no  executive  authority 
over  the  line  executives,  other  than  that  which  naturally 
belongs  to  them  by  reason  of  the  moral  effect  of  their  close 
association  with  the  head  of  the  department. 

Arranging  the  type  form  of  organization  in  chart  form 
results  in  the  arrangement  shown  in  Figure  35. 

It  is  generally  conceded  that  no  executive  should  have 
more  than  a  limited  number  of  subordinates  reporting  di- 
rectly to  him.  This  number  varies  with  circumstances,  but 
in  work  of  this  kind  should  not  exceed  ten  or  twelve  at  the 
outside,  as  there  is  such  a  volume  of  small  questions  requir- 


ORGANIZATION  OF  INSPECTION  DEPARTMENT          145 


I 


—  i 


— * 


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o 


111 


146  THE  CONTROL  OF  QUALITY 

ing  prompt  settlement,  to  say  nothing  of  the  demands  on 
the  chief  inspector's  time  for  continuous  constructive  work. 
Therefore  in  a  concern  making  several  lines  of  product, 
there  should  be  an  inspection  superintendent  (or  a  general 
foreman-inspector)  in  general  charge  of  each  group  of  shops. 
The  principal  assistant  to  the  chief  inspector  may  very 
well  be  one  of  these  superintendents.  On  the  chart  shown 
(Figure  35)  any  other  departments  that  may  be  assigned  to 
the  care  of  the  chief  inspector  (such  as  the  laboratories  for 
raw  material  inspection,  the  gage-checking  department,  etc.) 
should  be  added,  as  separate  main  divisions,  on  the  line  a-b. 
The  line  c-d  of  the  chart  provides  for  a  foreman-inspec- 
tor in  charge  of  each  production  department,  and  since  in- 
spection is  best  performed  when  strictly  specialized  accord- 
ing to  classes  or  kinds  of  work,  it  is  suggested  that  there  be 
a  separate  foreman  for  each  different  kind  of  production 
department  in  the  group,  even  if  this  results  in  considerable 
disparity  in  the  sizes  of  the  forces  reporting  to  the  various 
foremen-inspectors.  Thus  the  foreman-inspector  of  the 
woodworking  department  in  a  small-arms  factory  may  have 
several  shop  floors  under  his  care,  while  the  heat  treatment 
department  foreman-inspector  has  only  one.  In  other 
words,  the  inspection  organization  should  parallel  the  pro- 
duction organization  in  this  respect,  rather  than  attempt  to 
equalize  the  jobs  by  combining  different  small  departments 
under  one  head. 

Special  Value  of  Understudies 

It  is  specially  essential  in  inspection  work  that  under- 
studies be  designated  for  foremen-inspectors  and  their  more 
important  assistants.  This  arises  from  the  fact  that  the 
personnel  of  the  inspection  department's  supervisory  force 
must  be  relied  on  to  a  large  extent  to  see  that  standards  of 
quality  do  not  shift;  the  need  is  great  even  when  every  care 


ORGANIZATION  OF  INSPECTION  DEPARTMENT          147 

has  been  taken  already  to  fix  the  working  standards  as 
definitely  as  possible.  In  the  work  of  keeping  standards 
from  shifting,  the  inspection  foremen  accumulate  a  large 
body  of  knowledge  in  the  form  of  small  details,  which  can- 
not be  quickly  passed  on  from  man  to  man,  but  must  be 
absorbed  from  contact  with  the  work.  It  is  therefore  very 
important  that  the  organization  provide  for  continuity  in 
this  respect,  so  that  what  might  be  called  the  "complete 
standard"  will  be  carried  along  from  shift  to  shift  and  the 
gaps  caused  by  the  absence  of  any  member  of  the  super- 
visory force  safely  bridged. 

If  a  foreman-inspector  has  a  department  which  com- 
prises several  separate  floors  or  shops,  he  will  need  an  assist- 
ant in  each  shop.  This  man's  duties,  in  addition  to  main- 
taining discipline,  will  involve  a  continuous  checking  up  of 
the  inspection  work  going  on  in  the  shop,  deciding  doubtful 
cases — which  arise  principally  in  the  reinspection  of  rejected 
work — overseeing  the  care  of  gages,  and  attending  to  the 
orderly  storage  of  work  in  process.  Each  inspection  crib 
should  have  a  working  inspection  boss — that  is  to  say,  one 
of  the  ablest  inspectors  working  in  the  crib  should  be  desig- 
nated to  assume  general  charge  of  all  the  work  going  on  in 
the  crib.  The  working  force  in  each  crib  will  consist  gen- 
erally of  inspectors,  counters,  and  in  addition,  especially  if 
the  boxes  of  work  are  heavy  and  if  the  flow  of  work  is  rapid, 
a  common  laborer  or  two.  The  counters  are,  of  course, 
engaged  in  the  work  of  checking  up  the  quantity  of  work 
performed  on  operations  that  are  not  inspected,  and  are 
listed  separately  merely  to  indicate  that  this  work  should  be 
performed  at  a  lower  rate  of  pay  from  inspection  proper. 

Duties  of  Inspectors 

In  this  connection  it  may  be  noted  that  a  misunder- 
standing sometimes  arises  when  the  employment  department 


148  THE  CONTROL  OF  QUALITY 

hires  men  as  inspectors,  and  the  inspection  department  sub- 
sequently places  them  in  central  inspection  cribs  where  they 
may  have  to  do  more  physical  handling  and  lifting  of  boxes 
of  work  than  they  do  inspecting.  The  individual  thinks  he 
is  going  to  be  an  inspector,  but  finds  difficulty  in  distinguish- 
ing between  his  work  and  that  of  a  shop  laborer.  It  is  sug- 
gested that  this  difficulty  may  be  lessened  by  creating  the 
position  of  assistant  inspector  as  an  intermediate  step 
between  common  labor  and  bench  inspector.  If  the  em- 
ployment department  is  careful  to  make  clear  to  the  appli- 
cant what  his  duties  are  to  be,  there  is  less  chance  of  a 
misunderstanding  later  on. 

Central  inspection  is  usually  reinforced  by  a  small  group 
of  floor-inspectors.  These  men  should  be  of  a  higher  grade 
than  the  bench  inspectors  in  the  crib,  and  probably  higher 
even  than  the  working  foreman  of  the  crib,  since  their  duties 
are  performed  more  independently.  Consequently  they 
should  report  directly  to  the  assistant  foreman  in  charge  of 
inspection  in  the  shop,  and  not  to  the  crib  foreman. 

The  Chief  Inspector's  Staff 

It  was  remarked  on  page  144  that  the  chief  inspector's 
staff  should  have  no  executive  authority,  other  than  that 
which  accrues  to  them  by  reason  of  their  close  association 
with  the  chief  inspector.  The  latter  fact  will  naturally 
give  them  all  the  prestige  their  work  requires.  The  staff 
organization  should  be  laid  out  along  functional  lines  so  as 
to  provide  a  general  service  for  the  help  and  guidance  of  the 
line  executives.  It  must  secure  also,  for  the  assistance  of 
the  chief  inspector,  an  inspection  of  inspection,  without  de- 
stroying the  individual  responsibility  or  dividing  the  au- 
thority of  the  chief  inspector's  subordinate  executives.  Such 
division  of  authority  is  one  of  the  greatest  dangers  in  large 
organizations  of  combined  line  and  staff  type. 


ORGANIZATION  OF  INSPECTION  DEPARTMENT          149 

Thus  each  staff  assistant  will  be  a  carefully  selected 
specialist,  combining  the  work  of  an  instructor  in  his  line  of 
work  with  that  of  assisting  the  chief  inspector  in  checking 
up  his  assigned  part  of  the  work  throughout  the  entire  de- 
partment. The  staff  duties  to  be  performed  may  be  listed 
as  follows,  with  the  understanding  that  some  of  them  may 
be  combined  under  one  individual  where  the  volume  of  work 
warrants  it: 

1.  Personnel  matters,   including  the  investigation  of 

questions  affecting  pay,  promotion,  discharge,  as- 
signment of  new  employees,  etc.  This  work 
usually  requires  the  entire  time  of  one  man. 

2.  Follow-up  of  technical  instructions  from  the  chief 

inspector's  office  to  the  inspection  force,  including 
checking  up  the  adherence  to  prescribed  standards. 

3.  Care,  use,  and  custody  of  gages,  including  making 

sure  that  all  gages  pass  through  the  gage-checking 
department  as  scheduled. 

4.  Analysis  of  trouble  reports  from  the  foremen-in- 

spectors, especially  those  relating  to  technical 
difficulties  encountered  in  the  parts-making  shops 
and  in  the  assembling  department.  This  work 
includes  the  further  investigation  of  the  reports, 
also  seeing  that  the  more  important  ones  are 
placed  before  the  chief  inspector  to  bring  to  the 
attention  of  the  proper  authorities  in  the  general 
factory  organization. 

5.  Liaison  duty  with  the  production  engineer  to  see  that 

the  inspection  department  is  collecting  produc- 
tion data  for  him  in  a  satisfactory  manner. 

In  addition,  the  chief  inspector  frequently  has  small 
technical  matters  requiring  the  services  of  a  junior  engineer 
to  conduct  the  preliminary  investigation.  It  is  suggested 


150 


THE  CONTROL  OF  QUALITY 


ORGANIZATION  OF  INSPECTION  DEPARTMENT          151 

that  such  men  be  taken  from  time  to  time  from  the  rank  and 
file  of  the  inspection  force,  or  from  the  laboratories.  This 
practice  will  serve  to  broaden  the  men  in  question,  and  will 
accomplish  the  specific  purpose  in  hand  quite  as  well  as  if 
they  were  permanently  assigned  to  the  staff  of  the  chief 
inspector's  office.  Under  some  conditions,  as  a  more  or  less 
temporary  expedient  in  guiding  the  factory  toward  the  best 
compromise  required  by  the  commercial  situation,  the  chief 
inspector  may  be  given  a  staff  assistant  taken  from  the  sales 
department.  In  this  case  the  sales  department  may  be  re- 
garded as  the  purchaser  and  the  sales  representative  as  the 
purchaser's  inspector. 

The  Inspection  Department  Personnel 

Little  has  been  said  as  yet  about  the  qualities  to  be 
sought  for  in  choosing  men  for  the  duties  of  foremen-inspec- 
tors, their  assistants,  and  the  working  inspectors.  The 
problem  is  not  one  of  choosing  the  kind  of  men  who  are  best 
qualified,  but  rather  of  making  the  best  use  of  the  men  that 
are  available.  There  is  ' '  history ' '  in  the  statement,  as  more 
than  one  chief  inspector  can  testify  from  sad  experience  in 
recent  years. 

Some  of  the  men  who  take  employment  in  the  inspection 
department  have  had  previous  experience  in  technical  work, 
and  some  have  not.  If  the  experience  of  the  former  class 
has  resulted  in  a  self-sufficient  knowledge,  they  should  be 
replaced  by  men  of  the  class  who  have  no  such  technical 
experience,  and  know  that  they  do  not  have  it,  because  the 
inspectors  must  follow  the  standards  set,  without  modifying 
them  in  the  light  of  their  previous  experience.  In  other 
words,  obedience  to  orders  is  the  prime  desideratum. 

In  assigning  duties  in  the  inspection  department  organi- 
zation, therefore,  it  is  necessary  to  place  the  personnel  so  as 
to  grade  the  amount  of  discretion  to  be  allowed  in  matters 


152  THE  CONTROL  OF  QUALITY 

requiring  the  exercise  of  judgment.  It  might  be  said  that 
the  amount  or  quantity  of  judgment  to  be  applied  by  any 
individual  meniber  of  the  inspection  force  should  be  de- 
creased as  we  go  down  the  line  from  foreman-inspector  to 
the  inspector  working  in  the  crib. 

The  Bench  Inspector 

The  inspector  applying  gages  at  the  bench,  or  inspecting 
finish  as  to  sample,  should  be  the  kind  of  person  who  has 
reasonably  good  eyesight  and  tactile  sense ;  but  more  than 
this'  he  must  be  temperamentally  suited  to  doing  exactly 
what  he  is  told  to  do.  This  will  consist  in  sorting  the  work 
he  is  inspecting  into  work  that  is  clearly  according  to 
standard,  work  that  is  clearly  not  according  to  standard, 
and  work  about  which  he  is  doubtful,  leaving  the  decision 
as  to  the  latter  class  of  work  to  his  immediate  superior. 
As  stated  before,  this  process  implies  reasonably  definite 
standards  of  quality  in  the  first  place. 

The  Floor-Inspector 

The  floor-inspector  should  be  of  entirely  different  charac- 
ter. He  has  the  important  duty  of  first-piece  inspection 
before  he  authorizes  a  machine  to  begin  a  run  of  work.  In 
addition  he  may  be  given  the  right  to  order  a  machine 
stopped  if  the  work  is  not  to  his  satisfaction.  This  calls  for 
good  judgment  backed  up  by  practical  experience,  hence  the 
floor-inspector  is  usually  a  first-class  machinist,  to  whom  the 
title  and  duties  of  inspector  may  make  an  appeal,  or  who 
views  this  work  as  a  step  in  the  direction  of  a  foremanship  of 
some  sort — which  it  certainly  should  be. 

Salvaging  Native  Ability 

Practically  every  large  inspection  department  possesses 
a  unique  characteristic,  and  a  very  happy  one.  It  is  a  veri- 


ORGANIZATION  OF  INSPECTION  DEPARTMENT          153 

• 

table  "gold  mine"  of  men  possessing  unusual  native  ability 
and  good  character,  but  lacking  experience  in  factory  work. 
Every  once  in  a  while,  and  for  various  reasons  which  do  not 
matter,  some  man  decides  to  make  a  radical  change  in  his 
work.  His  very  lack  of  acquaintance  with  factory  life  may 
be  the  source  of  his  desire  to  try  it,  and  he  presently  appears 
at  the  factory  employment  office.  Having  no  knowledge  of 
machinery,  he  hesitates  to  attempt  machine  operation,  even 
if  the  way  is  made  easy  for  him  to  acquire 'the  necessary 
skill;  but  the  title  of  inspector  may  make  a  special  appeal, 
both  as  a  dignified  occupation  and  as  an  opportunity  to 
learn  more  about  manufacturing  methods  at  close  range. 
This  is  one  explanation  of  the  presence  of  such  men  in 
the  inspection  department.  As  to  where  they  are  to  be 
discovered,  the  answer  is,  obviously,  at  the  bench,  usually 
working  quietly  but  nevertheless  with  their  eyes  open  to 
what  is  going  on  around  them  in  the  shop.  Unless  the  fore- 
man is  an  unusually  human  sort  of  executive,  he  will  fail  to 
see  the  possibilities  in  these  subordinates.  Someone  higher 
up  must  keep  an  eye  out  for  such  men,  and  see  that  they  are 
given  the  chance  they  hoped  for  when  they  entered  the 
establishment. 

A  Case  in  Point 

The  circumstances  just  referred  to  came  to  my  attention 
for  the  first  time  a  few  years  ago,  in  the  course  of  reorganiz- 
ing an  inspection  service  of  some  2,000  employees,  where 
an  excessive  labor  turnover  in  this  department  was  con- 
sidered to  be  one  of  the  primary  reasons  for  defective  con- 
trol of  quality.  The  problem  of  reducing  the  turnover  was 
attacked  by  direct  action — the  chief  inspector  had  a  personal 
talk  with  every  man  entering  or  leaving  the  department. 
The  experience  was  somewhat  arduous,  but  this  was  more 
than  offset  by  the  results,  which  were  felt  almost  immediately. 


154  THE  CONTROL  OF  QUALITY 

A  certain  foreman-inspector  complained  regularly  and 
frequently  that  the  men  supplied  him  were  "  no  good."  The 
foreman  himself  was  a  man  of  long  experience  in  the  busi- 
ness, and  by  reason  of  this  fact  seemed  unable  to  adjust 
himself  to  the  necessity  of  training  the  men  supplied  him 
rather  than  expecting  to  find  men  already  skilled  in  their 
work — a  situation  resulting  from  the  war  time  labor  condi- 
tion. Most  of  the  men  leaving  his  department  gave  every 
reason  but  the  right  one  for  quitting,  probably  in  the  fac- 
tory spirit  of  being  good  losers.  Presently,  however,  a  man 
appeared  in  the  chief  inspector's  office  on  his  way  out. 
Character  and  personality  were  written  plainly  on  his  face. 
Under  pressure  he  told  his  story,  and  in  a  detail  that  showed 
a  keen  grasp  of  conditions. 

Briefly,  the  story  was  this.  After  completing  a  semi- 
technical  college  course,  he  had  taken  a  political  job,  and  by 
an  unlucky  swing  of  the  political  pendulum  about  fifteen 
years  later  found  himself  under  the  necessity  of  seeking 
other  means  of  supporting  his  family.  So  he  turned  to  this 
particular  factory  because  he  had  heard  of  possible  opportu- 
nities there.  It  looked  to  him  like  a  fresh  start  with  good 
chances  for  a  satisfactory  career.  After  three  months  at 
the  bench  as  an  inspector  he  confessed  that  he  knew  little 
more  about  the  intricacies  of  the  business  than  when  he 
started.  What  he  did  know,  he  had  been  forced  to  dig  out 
by  himself  without  encouragement  from  above.  On  the 
other  hand,  he  knew  what  was  basically  wrong  in  that  shop 
better  than  the  foreman-inspector  himself. 

This  experience  was  the  cause  of  starting  a  school  for 
such  men  under  an  old  foreman  who  possessed  a  heart  as 
well  as  a  head,  and  who  passed  on  enough  of  his  practical 
knowledge  to  enable  his  pupils  to  qualify  as  tool-setters  and 
gang  bosses.  After  this,  promotion  was  up  to  the  individual, 
but  he  was  always  encouraged  to  bring  his  problems  back  to 


ORGANIZATION  OF  INSPECTION   DEPARTMENT          155 

his  old  instructor  for  helpful  advice.  The  man  whose  case 
was  just  referred  to  became  assistant  superintendent  of  a 
large  production  department  in  about  six  months  from  the 
time  when  he  was  ready  to  give  up  in  disgust  and  discourage- 
ment. Several  other  men,  discovered  in  the  same  way,  were 
developed  into  excellent  foremen  instead  of  being  lost  to  the 
organization. 

Study  the  Individual 

All  of  which  suggests  that  while  the  individual  unit  of 
an  organization  may  be,  in  one  sense,  part  of  a  machine,  he 
nevertheless  is  a  man,  with  all  of  the  perfectly  natural  limi- 
tations and  variable  potentialities  of  a  human  being.  I  ven- 
ture to  say  that  there  is  nothing  in  the  entire  work  of  organiz- 
ing and  running  the  inspection  department  (not  to  mention 
the  rest  of  the  factory)  that  will  yield  so  large  a  return,  both 
in  actual  accomplishment  and  in  personal  satisfaction,  as 
the  study  of  the  men  themselves. 


CHAPTER  X 

MANAGEMENT  OF  THE  INSPECTION 

DEPARTMENT 
The  Task 

The  chief  end  to  be  sought  in  the  management  of  the  in- 
spection department  is  to  obtain  a  firm  control  of  quality 
by  holding  the  work  to  definite  predetermined  standards; 
and  to  accomplish  this  with  the  maximum  of  economy.  The 
task  presents  at  least  two  essential  differences  from  the 
management  of  a  production  department  of  commensurate 
size: 

1 .  The  working  force  is  widely  scattered  and  the  work 
unusually  varied.     Co-ordination  is  difficult. 

2.  The  pay  of  inspectors  is  nearly  always  low  in  propor- 
tion to  their  responsibilities,  with  attendant  difficulty  in 
attracting  and  keeping  the  right  kind  of  labor. 

Co-ordination 

The  first  step  in  co-ordinating  the  work  of  the  inspection 
department  is  to  see  that  the  chief  inspector's  office  is  lo- 
cated as  nearly  as  may  be  in  the  center  of  the  plant.1  The 
inspection  force  is  concerned  with  every  manufacturing 
process  going  on  in  the  factory  and  with  many  of  the  general 
service  departments.  It  reaches  into  every  part  of  the  plant. 
Questions  arise  every  hour  of  the  day  that  call  for  settle- 
ment by  personal  conference  with  the  chief  inspector  or  some 
member  of  his  staff.  Much  time  and  effort  will  be  saved  by 
lessening  the  average  distance  to  the  point  of  trouble. 
Furthermore  it  is  greatly  to  be  desired  that  both  production 
and  inspection  department  executives  feel  that  the  chief 

1  In  the  author's  opinion,  the  same  statement  is  true  for  all  executive  and  managerial  de- 
partments. See  "Production  as  Affected  by  Size  of  Plant,"  by  G.  S.  Radford,  Management 
Engineering,  Aug.  1921. 

156 


MANAGEMENT  OF  INSPECTION  DEPARTMENT  157 

inspector  is  in  as  close  contact  with  the  work  as  they  are 
themselves.  The  chief  inspector's  job  is  not  in  the  front 
office,  but  rather  in  the  very  heart  of  the  works.  Moreover 
it  is  in  every  way  a  more  sociable  arrangement,  and  that  is 
desirable. 

The  Use  of  Conferences 

In  co-ordinating  the  efforts  of  his  own  executives,  the 
chief  inspector  will  find  use  for  all  of  the  ordinary  devices 
of  good  management.  He  will  find  conferences  with  his 
superintendents  and  foremen  of  special  value. 

Incidentally  the  main  purpose  of  the  conferences  will  be 
obtained  more  surely  if  the  chief  inspector  does  not  do  all 
the  talking.  The  men  in  the  room  will  be  brought  together 
better  if  they  come  to  accept  the  conference  as  an  opportu- 
nity to  obtain  the  help  of  several  minds  in  working  out  their 
immediate  and  most  baffling  problems.  The  chief  can 
soon  develop  good  fellowship  and  a  common  interest  in  the 
work  of  the  entire  inspection  department,  by  a  little  adroit 
steering. 

A  conference  of  his  immediate  subordinates  once  a  week 
will  be  sufficient  under  ordinary  circumstances,  but  it  is 
suggested  that  this  practice  be  supplemented  by  an  occa- 
sional conference  with  the  inspection  executives  of  each  in- 
spection group,  for  the  principal  purpose  of  developing  a 
closer  personal  contact  and  acquaintance  between  the  sub- 
ordinate executives  and  the  chief  of  their  department.  For 
the  entire  department  should  be  in  harmony  with  the  chief's 
policies  and  therefore  quick  to  react  to  his  instructions  as 
they  are  passed  down  the  line.  Such  flexibility  of  control 
will  be  strengthened  more  certainly  by  personal  acquain- 
tance and  through  frequent  contact  the  personality  of  the 
head  of  the  department  will  be  reflected  in  the  department 
as  a  whole. 


158  THE  CONTROL  OF  QUALITY 

Letters  of  Instruction  and  Advice 

It  will  be  found  to  be  an  excellent  plan,  in  co-ordinating 
the  various  units,  if  each  foreman  and  staff  employee  is 
supplied  with  a  simple  letter-size  binder  for  keeping  a  file  of 
department  bulletins.  These  bulletins  should  be  issued 
from  time  to  time  from  the  chief  inspector's  office  as  a  quick 
means  of  conveying  his  executive  instructions  to  the  entire 
organization,  defining  his  policies  and  supplying  technical 
information.  The  book  should  be  kept  on  the  foreman's 
desk  for  the  subforemen  to  read,  and  it  should  be  the  duty 
of  one  of  the  staff  assistants  to  question  the  subforemen 
occasionally  about  the  messages  in  the  bulletins  which 
specially  concern  their  work,  so  as  to  encourage  them  to 
keep  in  touch  with  the  plans  and  policies  of  the  department. 
The  scheme  will  not  work  unless  it  is  closely  followed  up, 
but  it  can  be  made  a  most  potent  force  in  keeping  men  ' '  on 
their  toes"  and  working  harmoniously,  especially  if  the  bul- 
letins or  instruction  notices  are  explained  and  discussed  in 
conference. 

Finally,  it  is  in  the  general  work  of  helping  to  keep  the 
entire  department  pulling  together  smoothly,  that  the  mem- 
bers of  the  chief  inspector's  staff  will  justify  their  employ- 
ment. To  make  their  work  most  effective,  the  chief  should 
encourage  them  to  confer  with  him.  Whenever  practicable 
they  should  make  their  headquarters  in  the  chief's  office. 

Reduction  of  Turnover  of  Inspection  Force 

No  matter  how  thoroughly  standards  of  quality  are 
specified,  there  will  be  a  certain  amount  of  incompleteness 
in  the  statement  of  them  that  can  be  filled  out  only  from 
the  accumulated  experience  of  the  inspector.  Again,  it  re- 
quires a  varying  length  of  time  for  any  inspector  to  acquire 
the  technique  necessary  to  apply  a  given  gage  with  the  de- 
sired accuracy  and  skill,  or  to  conduct  satisfactorily  any 


MANAGEMENT  OF  INSPECTION  DEPARTMENT  159 

given  inspection  operation.  Because  of  these  reasons  it  is 
important  that  the  personnel  of  the  inspection  force  be  as 
permanent  as  that  of  other  departments,  or  even  more 
permanent,  if  standards  of  quality  are  to  be  prevented  from 
fluctuating.  This  is  in  addition  to  the  usual  loss  in  quan- 
tity of  work  performed,  due  to  excessive  labor  turnover  in 
any  class  of  work.  The  disparity  in  pay  already  referred  to 
is  a  disturbing  element  and  the  turnover  in  a  large  inspec- 
tion department  is  likely  to  be  unduly  high  in  consequence. 
Obviously,  the  primary  action  to  take  in  order  to  stabi- 
lize conditions  is  to  employ  people  for  inspection  work  who 
are  most  likely  to  take  to  it  kindly.  For  example,  the  in- 
spection work  is  usually  less  strenuous  than  the  operation  of 
manufacturing  machines,  which  indicates  the  employment 
of  people  (frequently  women)  who  cannot  stand  the  physical 
strain  of  the  heavier  production  work,  and  know  it. 

Provision  for  Promotion 

When  a  relatively  high  degree  of  experience  and  skill  are 
requisite,  as  in  the  case  of  floor-inspectors,  there  should  be 
assurance  that  the  inspection  force  will  share  in  promotions 
to  assistant  foremanships  in  the  production  departments,  so 
that  the  inspectors  have  something  to  look  forward  to  when 
higher  vacancies  are  to  be  filled. 

Since  the  easier  way  of  the  direct  financial  incentive  is 
mostly  barred,  resort  must  be  had  to  every  possible  non- 
financial  incentive.  That  is  to  say,  in  brief,  that  the  inspec- 
tion department  must  be  handled  so  that  it  will  come  to  be 
recognized  as  an  excellent  place  in  which  to  work — and  more 
important  yet,  a  force  that  a  man  should  be  proud  to  belong 
to.  The  work  can  be  made  pleasant  if  the  inspector  is 
treated  by  his  executives  with  just  a  little  more  friendliness 
and  courtesy  than  is  customary  in  shops.  I  do  not  mean  to 
imply  that  his  job  should  be  made  a  soft  one.  On  the  con- 


160  THE  CONTROL  OF  QUALITY 

trary,  the  spirit  of  the  organization,  and  hence  the  dignity  of 
the  work,  will  be  greatly  enhanced  by  stressing  the  value  of 
character,  by  cultivating  a  pride  of  achievement  in  terms  of 
accuracy,  and  by  a  rigorous  demand  for  personal  responsi- 
bility. But  all  of  this  should  be  tempered  by  a  very  obvious 
interest,  on  the  part  of  the  chief  inspector  and  his  assistants, 
in  the  personal  welfare  and  interest  of  everyone  in  the  de- 
partment. If  this  takes  only  the  form  of  an  evident  will- 
ingness to  help  the  other  fellow  to  help  himself,  the  object 
sought  will  be  attained.  All  parties  gain — the  executive  by 
having  a  more  contented  and  efficient  force,  and  the  sub- 
ordinate by  having  a  conscious  increase  in  satisfaction  in  his 
work,  through  the  knowledge  that  his  value  to  himself  and 
to  others  is  growing  all  the  time. 

Wages 

Owing  to  the  fact  that  it  rarely  is  practicable  to  measure 
the  work  performed  by  inspectors,  it  is  the  general  practice 
to  pay  them  on  the  day-wage,  or  hourly  wage  basis.  It 
frequently  occurs  that  the  inspection  work  must  be  per- 
formed in  a  shop  where  the  machine  operators  are  paid  on  a 
piece  work  or  similar  system  based  upon  the  quantity  of 
work  performed.  Hence  it  is  not  unusual  to  find  a  situa- 
tion arising  where  ordinary  machine  operators  are  paid  at 
rates  considerably  in  excess  of  those  paid  the  men  who  in- 
spect their  work,  and  under  such  circumstances,  there  is 
more  than  the  usual  difficulty  in  keeping  the  inspection  force 
in  a  contented  frame  of  mind. 

The  easiest  apparent  cure  is  to  raise  the  wage  scale  for 
inspectors,  but  that  way  is  rarely  open,  in  spite  of  the  fact 
that  the  inspectors  perform  work  in  many  cases  that  is 
worth  enough  to  warrant  a  higher  scale.  An  economy  in 
total  cost  might  conceivably  be  attained  thereby,  but  in 
nearly  every  plant,  inspection  is  regarded  as  a  necessary 


MANAGEMENT  OF  INSPECTION  DEPARTMENT  l6l 

but  regrettable  and  non-productive  expense.  Consequently 
the  chief  inspector  is  faced  with  the  problem  of  doing  the 
best  he  can  with  a  strictly  limited  pay-roll,  and  therefore  is 
forced  to  use  the  lowest  rate  of  wages  that  will  keep  him  sup- 
plied with  a  grade  of  labor  that  will  do. 

As  a  result  the  chief  inspector  and  his  foremen  will  be 
besieged  with  requests  for  raises  in  pay,  and  a  relative  de- 
gree of  contentment  can  be  obtained  only  by  having  a 
definite  rate  of  promotion  with  graded  rates  of  pay  based 
upon  length  of  service  in  combination  with  efficient  work. 
This,  I  believe,  has  been  found  to  be  the  best  solution  under 
the  day- wage  system  for  all  kinds  of  work.  I  have  seen  the 
labor  turnover  actually  decreased  by  the  flat  announcement 
that  no  increase  in  pay  would  be  considered  for  sixty  days, 
and  this  in  the  face  of  insistent  demands  for  raises.  In  this 
instance,  however,  there  had  been  no  systematic  arrange- 
ment for  graded  increases,  so  that  the  practice  of  asking  for 
raises  had  grown  up,  with  the  net  result  that  the  granting  of 
one  request  only  served  to  encourage  others. 

Piece  Work  in  Inspection 

It  is  believed  that  inspectors  working  on  small  pieces 
can  be  paid  piece  work  to  advantage  in  many  more  cases 
than  would  ordinarily  be  supposed;  but  this  system,  obvi- 
ously, can  only  be  used  to  advantage  when  the  work  war- 
rants a  check  inspection,  or  inspection  of  inspection  by 
sampling  all  work  after  the  piece  working  inspectors  have 
gone  over  it.  When  this  can  be  done  without  sacrificing 
quality,  the  usual  economy  inherent  in  the  piece  work  sys- 
tem will  be  experienced,  although  the  individual  worker 
makes  more  money.  Inspectors  employed  on  piece  work, 
however,  must  be  penalized  strictly  by  non-payment  for  any 
boxes  of  work  found  to  contain  defective  parts,  and  less 
heavily  for  the  rejection  of  good  parts. 
11 


162  THE  CONTROL  OF  QUALITY 

Working  Hours 

Another  potential  source  of  discontent  arises  from  the 
fact  that  at  least  a  part  of  the  inspection  force  will  need  to 
be  on  hand  both  before  and  after  the  regular  working  hours. 
It  is  especially  important  that  the  inspection  cribs  be  ready 
to  issue  work  before  the  beginning  of  work  in  the  shop — 
sufficiently  early,  indeed,  to  make  sure  that  all  machine 
operators  are  supplied  with  work  well  ahead  of  time.  Other- 
wise the  production  force  have  a  valid  cause  for  complaining 
that  they  are  delayed  in  getting  to  work  promptly.  Then 
again,  it  is  often  desirable  that  work  turned  in  at  quitting 
time  should  be  inspected  at  once.  When  choke-points 
occur  this  may  be  imperative.  The  suggestion  is  offered 
that  much  unnecessary  hard  feeling  can  be  stopped  by  a 
definite  understanding,  at  the  time  of  employment,  that  the 
working  hours  of  inspectors  will  be  staggered  a  little  out  of 
phase  with  the  regular  shop  working  hours.  The  total  time 
can  be  adjusted  by  allowing  a  longer  time  for  lunch  and  by 
a  reasonable  leniency  in  days  off.  The  time  outside  of 
regular  hours  need  not  exceed  15  minutes  in  most  cases,  so 
that  adjustments  of  total  time  are  not  difficult.  Needless 
to  say,  overtime  should  be  avoided  with  care,  as  both  costly 
and  conducive  to  the  creation  of  additional  and  needless 
overtime. 

The  Cost  of  Inspection 

Most  chief  inspectors  will  agree  that  the  average  fore- 
man-inspector, by  reason  of  his  being  a  foreman-inspector 
and  concurrently  with  his  assumption  of  that  duty,  at  once 
develops  an  unusual  ability  to  ask  for  more  inspectors,  and 
for  better  inspectors,  and  for  more  gages.  Now  as  all  of 
these  things  cost  money,  which  is  a  relatively  rare  commodity 
in  so  far  as  the  chief  inspector's  disbursements  are  permitted 
to  go,  some  other  way  out  must  be  found.  For  example, 


MANAGEMENT  OF  INSPECTION  DEPARTMENT  163 

the  foreman  may  be  shown  that  more  men  does  not  neces- 
sarily mean  a  corresponding  increase  in  the  amount  of  work 
performed.  Thus  in  the  curve  shown  in  Figure  37 — in  which 
the  abscissae  represent  the  total  number  of  men  in  the  work- 
ing force,  and  the  ordinates  represent  the  total  amount  of 
work  performed — it  is  not  unnatural  to  assume  that  output 
will  increase  in  direct  proportion  to  the  number  of  people 


O 

1" 


No.  of  Men 
Figure  37.     Curve  of  Output  and  Number  of  Men 

engaged  in  the  work,  as  shown  by  the  line  OA — the  more 
men,  the  greater  the  total  output. 

As  a  matter  of  fact,  a  little  consideration  will  show  that 
the  curve  OB C  is  more  nearly  true  for  any  given  job,  for  the 
reason  that  a  point,  B,  is  soon  reached  where  additional 
help  only  interferes  with  the  people  already  at  work,  until 
at  C  the  shop  is  so  crowded  that  no  one  can  move,  and  the 
output  returns  to  zero  again.  Hence  it  follows  that  for  any 
given  output,  OD,  there  are  two  limiting  numbers  of  men, 
DE  and  DF.  It  is  the  painful  lot  of  the  inspection  depart- 


1 64  THE  CONTROL  OF  QUALITY 

ment  to  work  a  little  inside  of  the  number  of  men  indicated 
by  the  point  E.  This  may  not  be  entirely  convincing  to 
your  foreman,  but  it  at  least  shows  them  what  they  are  up 
against  in  asking  for  more  men. 

Teaching  Inspectors 

Rather  than  engaging  more  men,  therefore,  it  is  a  mat- 
ter of  increasing  the  efficiency  of  the  allowable  force  and 
here  it  may  be  noted  as  a  fortunate  circumstance  that  in- 
spection work  lends  itself  readily  to  very  marked  economies 
in  the  way  of  greater  output  per  man,  through  the  applica- 
tion of  many  of  the  devices  of  modern  methods  of  manage- 
ment. This  is  especially  true  of  bench  inspection,  under 
the  conditions  of  central  inspection.  The  device  of  greatest 
utility  is  a  carefully  planned  use  of  sampling,  insuring  that 
no  more  work  is  done  than  is  necessary.  Next  comes  the 
matter  of  instruction  in  the  work  of  inspection,  to  see  that 
each  inspector  knows  just  what  he  is  trying  to  do,  and  the 
quickest  and  easiest  way  to  do  it.  There  are  so  many 
operations  in  inspection  work  which  appear  very  simple, 
that  there  is  a  strong  tendency  to  show  a  new  employee 
what  he  has  to  do  in  a  very  casual  and  general  sort  of  way 
and  then  leave  him  to  his  own  devices.  The  application  of 
a  gage  or  two,  or  a  viewing  for  surface  finish,  appears  to  be 
transparently  easy,  but  the  mental  attitude  that  regards 
any  piece  of  work  as  simple  is  a  danger  signal.  It  should 
be  borne  constantly  in  mind  that  time  and  motion  .study 
began  with  handling  pig  iron  and  shoveling  earth.  It  is  not 
unlikely,  in  fact,  that  the  most  striking  economies  are  to  be 
realized  in  the  most  simple  operations. 

The  instruction  of  inspectors  is  a  staff  job — that  is,  it 
should  be  a  staff  job  if  the  best  results  are  to  be  obtained. 
Perhaps  this  conclusion  flows  from  the  proverbial  truth  that 
work  which  is  left  to  everybody  is  rarely  done  right. 


MANAGEMENT  OF  INSPECTION   DEPARTMENT  165 

Combine  Instruction  with  Staff  Supervision 

The  instruction  should  be  combined  with  the  work  of 
one  of  the  technical  men  on  the  chief  inspector's  staff,  as  it 
fits  in  well  with  a  critical  examination  of  each  inspection 
point  taken  seriatim  and  somewhat  as  follows: 

1.  Is  the  measuring  device,  gage,  or  what-not,  such 

that  true  results  can  be  obtained? 

2.  Is  the  gage  being  applied  so  as  to  obtain  true  results? 

3.  Is  the  work  being  done  in  a  way  to  secure  the  great- 

est economy  of  inspection? 

The  first  two  questions  are  vital,  naturally,  since  money 
spent  upon  inspection  is  worse  than  wasted  if  the  results  are 
not  close  to  the  truth.  The  third  question  opens  up  the 
whole  field  of  possible  increase  of  efficiency.  Frequently, 
in  fact,  the  most  cursory  use  of  motion  study  reveals  large 
possibilities  for  saving  time  in  inspection,  especially  if  the 
inspector  considers  himself  under  the  necessity  of  hurrying. 
The  most  frequent  loss  arises  from  improper  placing  of  the 
boxes  of  work,  so  that  unnecessary  and  overcrossing  motions 
are  made.  Then  there  are  the  losses  that  arise  from  awk- 
ward posture  and  clumsy  holding  of  the  gage.  It  sometimes 
happens  that  a  separate  support  for  the  gage  will  help  mat- 
ters by  leaving  free  both  of  the  inspector's  hands.  In  this 
case  attention  should  be  given  to  seeing  that  the  support  is 
flexible  enough  to  permit  automatic  adjustment  of  a  close 
limit  gage  to  the  work. 

A  large  saving  can  be  secured  through  spreading  the 
message  of  careful  handling  of  both  work  and  gages.  Pre- 
cision instruments  and  fine  work  call  for  a  certain  amount 
of  gentleness,  of  the  sort  that  the  late  A.  J.  Corbesier,  the 
honored  fencing  master  at  Annapolis,  referred  to  when  he 
said,  "  Hold  your  foil  as  you  would  a  bird — firmly,  so  it  will 
not  escape;  gently,  so  it  will  not  be  hurt." 


1 66  THE  CONTROL  OF  QUALITY 

I  recall  an  experience  in  a  munition  plant,  where  a  room 
full  of  foreign  help  was  engaged  in  the  inspection  of  high- 
grade  work.  The  gages  were  applied  with  such  enthusiasm, 
and  highly  finished  parts  were  thrown  into  tote  boxes  with 
such  vigor  that  the  anvil  chorus  would  not  have  had  a  chance 
to  be  heard.  The  ordinary  bench  inspector  or  machine 
operator  in  our  larger  factories  will  easily  fall  into  almost  as 
bad  habits  unless  he  is  cautioned  continually. 

Unskilled  Help  in  Inspection 

Turning  now  to  one  of  the  greatest  economies  in  inspec- 
tion, especially  in  central  inspection  as  previously  stated ;  it 
is  not  necessary  (except  in  certain  kinds  of  floor-inspection) 
to  have  a  personnel  already  skilled  in  the  work  of  inspecting. 
In  fact  it  is  quite  inadvisable  to  employ  such  people  when 
the  object  is  to  limit  the  use  of  judgment  and  to  hold  to  a 
close  standard.  But  the  employment  of  unskilled  help 
again  indicates  the  necessity  of  providing  adequate  instruc- 
tion, not  alone  by  teaching,  which  always  should  be  a  large 
factor  in  management,  but  also  by  providing  accessible  ref- 
erence data,  such  as  samples,  large-scale  drawings  with 
gaging  points  distinctly  marked,  gage  instruction  cards,  and 
so  on.  It  should  not  be  necessary  to  mention,  except  for 
completeness,  how  important  it  is  to  begin  this  educational 
work  as  soon  as  the  new  inspector  is  employed.  There  are 
obvious  advantages  in  "catching  them  young."  The  work 
will  be  done  more  certainly,  and  probably  better  and  quicker, 
if  it  is  followed  up  by  a  staff  assistant. 

Female  Labor  for  Inspection  Work 

In  speaking  of  the  use  of  unskilled  labor  as  a  measure  of 
economy  in  inspection,  the  question  of  using  female  labor 
deserves  serious  consideration.  In  fact,  if  female  labor  is 
carefully  selected  with  reference  to  the  adaptability  of  the 


MANAGEMENT  OF  INSPECTION  DEPARTMENT 


16; 


Figure  38.     Prestwich  Fluid  Gage  as  Used  to  Inspect  Piston  Pins 
Diameter  held  to  within  0.0002  inch — Packard  Motor  Car  Company. 


168  THE  CONTROL  OF  QUALITY 

individual  to  the  class  of  work  involved,  it  will  be  found  that 
women  are  able  to  do  many  more  kinds  of  inspection  work 
than  might  be  supposed,  also  that  they  almost  invariably 
perform  it  better  than  men.  A  higher  grade  of  tactile  sense 
and  skill  can  be  secured  for  the  same  investment,  together 
with  a  stricter  compliance  with  instructions  in  the  matter  of 
holding  to  standard.  The  advantage  to  be  gained  in 
greater  contentment  of  the  inspection  force  alone,  makes  the 
employment  of  women  highly  desirable  whenever  possible. 

It  is  realized  that  many  factory  executives  hesitate  to 
introduce  women  into  the  inspection  department  in  shops 
where  none  but  men  are  employed  at  the  machines,  and  this 
for  reasons  quite  apart  from  their  suitability  for  such  inspec- 
tion work.  It  may  be  stated  as  a  fact,  however,  that  the 
feeling  is  not  warranted  if  proper  measures  are  taken  at  the 
start  to  maintain  discipline ;  for  the  presence  of  women  may 
be  made  to  secure  an  elevation  of  the  entire  tone  of  the  shop. 
To  do  this  requires  that  the  subordinate  inspection  bosses 
be  chosen  from  among  the  most  dignified  inspectors  and  that 
they  be  duly  impressed  with  the  importance  of  their  work. 
It  should  be  made  a  fixed  rule  also,  that  questions  affecting 
inspection  be  taken  up  by  the  production  bosses  with  the 
male  foreman  only. 

In  a  large  factory  employing  at  the  time  none  but  men 
in  the  shops,  female  help  to  the  number  of  several  hundred 
were  introduced  into  the  inspection  department  in  the  en- 
deavor to  stabilize  labor  turnover  in  the  department,  as  well 
as  to  secure  better  control  of  the  technique  of  inspection. 
Because  of  the  class  of  labor  in  the  plant,  the  management 
realized  that  matters  might  arise  which  would  be  reported  to 
them  more  certainly,  and  perhaps  more  easily  and  gracefully, 
if  the  women  could  carry  their  troubles  to  a  woman  rather 
than  to  a  man.  It  was  recognized,  besides,  that  a  high 
standard  of  character  in  the  inspection  department  was 


MANAGEMENT  OF  INSPECTION  DEPARTMENT  169 

worth  a  great  deal  in  controlling  the  quality  of  the  factory 
output.  With  this  in  mind,  one  of  the  secretaries  in  the 
main  office,  who  had  been  a  working  girl  and  who  combined 
rare  judgment  with  a  very  human  sympathy  for  her  asso- 
ciates, was  asked  to  take  the  time  to  become  acquainted 
with  at  least  one  or  two  girls  in  each  inspection  group.  The 
plan  proved  to  be  an  unqualified  success,  although  it  resulted 
in  the  dismissal  of  a  foreman  or  two,  and  a  few  of  the  inspec- 
tion force,  very  shortly  after  the  facts  began  to  come  in  and 
investigations  were  made.  It  was  not  long,  however,  before 
that  particular  plant  achieved  the  reputation  among  work- 
ing people  of  being  the  safest  factory  in  the  state  to  which  to 
send  their  daughters  for  employment. 

Women  as  inspectors  will  be  found  to  work  faster  than 
men,  especially  if  their  strength  is  conserved  by  providing 
men  to  do  the  heavier  work  of  lifting  and  moving  tote  boxes. 
The  amount  saved  is  sufficient  to  pay  for  the  greater  com- 
forts in  the  way  of  chairs,  recreation  and  rest  rooms,  and 
other  conveniences,  that  must  be  provided  for  women.  It 
should  be  remembered,  however,  that  women  inspectors 
should  be  required  to  adapt  their  dress  to  secure  personal 
safety,  by  wearing  caps  and  suitably  protected  sleeves,  as 
in  the  case  of  female  machine  operators;  for  even  women 
inspectors  are  occasionally  passing  near  machinery  in 
motion. 

Women  Inspectors  on  Heavy  Work 

From  the  technical  standpoint,  there  are  many  kinds  of 
work  not  ordinarily  inspected  by  women  which  could  be  so 
handled  to  advantage,  even  in  the  case  of  comparatively 
heavy  pieces.  This  requires  that  the  individual  be  chosen 
for  the  job  and  given  a  preliminary  course  of  training.  The 
inspection  of  the  interior  of  rifle  barrels  has  been  performed 
by  women  to  great  advantage,  although  it  is  technically 


170  THE  CONTROL  OF  QUALITY 

difficult  and  the  physical  work  of  holding  them  up  to  the 
light  is  tedious,  to  say  the  least.  In  the  case  I  have  in  mind , 
the  inspectors  were  chosen  from  among  a  number  of  obvi- 
ously robust  and  sturdy  individuals,  whose  eyesight  meas- 
ured very  nearly  perfect.  They  were  then  instructed  in  the 
art  by  an  expert  foreman  who  believed  that  women  could  be 
taught  to  do  the  work.  It  took  ten  days  to  graduate  them, 
and  it  only  remains  to  be  stated  that  they  developed  a  pro- 
ficiency that  at  first  set  too  high  a  standard.  It  would,  in 
fact,  have  tied  up  production,  if  prompt  measures  had  not 
been  taken  to  reinspect  their  rejects,  until  they  could  be 
taught  to  hold  to  a  more  reasonably  commercial  standard. 
And  in  spite  of  this  experience  the  scheme  was  nearly  wrecked 
by  their  inspection  foreman  (a  man  of  long  experience  and 
great  skill  in  the  business),  who  stubbornly  refused  to  be- 
lieve that  women  could  learn,  in  so  short  a  time,  work  re- 
quiring such  skill.  From  this  fact  the  reason  may  be  de- 
duced for  emphasizing  certain  words  in  this  paragraph.  It 
may  possibly  suggest  in  addition,  that  there  is  more  than  a 
modicum  of  "bunk"  about  many  skilled  operations,  so- 
called,  as  is  rapidly  discovered  when  the  problem  of  con- 
trolling them  is  approached  in  a  truly  scientific  manner. 

Morale 

No  treatment  of  the  management  of  the  inspection  de- 
partment should  close  without  stressing  the  special  value 
of  a  high  morale.  Just  as  the  precision  of  measuring  instru- 
ments is  fundamental  in  determining  the  degree  of  mechani- 
cal accuracy  that  may  be  attained,  so  must  fidelity  to  truth 
be  developed  in  the  inspection  force,  to  secure  the  predeter- 
mined standard  of  quality  that  is  desired.  Thus  character 
is  the  first  desideratum,  and  as  a  necessary  element  of  it, 
impartiality,  thoroughness,  and  accuracy  in  developing  the 
real  facts,  and  courage  in  bringing  them  to  light.  The  chief 


MANAGEMENT  OF  INSPECTION  DEPARTMENT  171 

inspector  must  train  his  people  to  secure  this  result;  and 
then,  lest  he  lose  the  advantage,  he  must  support  them  when 
they  are  right,  and  must  in  his  turn  be  supported  by  his 
superiors  in  the  management.  Concurrently,  the  inspec- 
tion force  should  be  disciplined  to  a  strict  obedience  in 
carrying  out  the  chief's  instructions,  if  for  no  other  reason 
than  to  secure  a  quick  flexibility  and  certainty  of  control  in 
developing  the  standards  of  quality,  with  freedom  from  dis- 
turbing influences  arising  outside  of  the  inspection  depart- 
ment. 

The  presence  of  this  same  discipline,  administered  always 
with  personal  courtesy,  will  build  up  the  individual's  sense 
of  the  value  of  his  work  to  the  entire  organization;  and  with 
the  resulting  realization  of  personal  dignity  and  knowledge 
of  trust,  there  will  come  a  feeling  of  responsibility  and  pride 
in  the  work  of  the  whole  department — that  is  to  say,  an 
esprit  de  corps. 


CHAPTER  XI 
INSPECTION  IN  PRACTICE 

Type  Varies  with  Individual  Factory 

The  development  of  a  philosophy  of  inspection  requires 
that  its  principles  be  stated  somewhat  in  the  form  of  abstract 
generalizations.  It  is  believed,  as  has  been  stated,  that 
these  principles  are  of  much  wider  application  than  is  gen- 
erally appreciated  and  that  industry  would  benefit  greatly 
if  they  were  followed  much  more  closely  in  practice.  It  is 
equally  true,  however,  that  the  translation  of  these  prin- 
ciples into  action,  as  has  been  pointed  out  in  several  in- 
stances, requires  that  they  be  interpreted  with  a  leaven  of 
common  sense,  and  applied  in  the  form  of  whatever  adap- 
tation is  economically  most  suitable  for  the  particular  case 
involved. 

Each  manufacturing  enterprise  has  its  own  peculiar  con- 
ditions to  meet,  and  the  arbitrary  introduction  of  a  fixed 
system  of  any  sort,  without  careful  and  intelligent  modifica- 
tion, is  fraught  with  grave  dangers.  "What  is  one  man's 
meat  is  another's  poison." 

If  the  management  is  critically  introspective,  so  to  speak, 
the  way  in  which  inspection  is  organized  and  applied  is  likely 
to  be  well  suited  to  the  needs  of  the  factory.  Hence  the 
value  of  studying  the  inspection  methods  of  well-established 
industries,  whose  successful  operation  may  be  taken  for 
granted.  Such  study  is  the  purpose  of  the  present  chapter. 
As  an  introduction  thereto  the  various  modifying  consid- 
erations which  are  involved  in  special  cases  may  now  be 
assembled. 

172 


INSPECTION  IN  PRACTICE  173 

When  to  Use  Extensive  Inspection 

Briefly  stated,  the  most  extensive  and  complex  use  of 
inspection  is  desirable  when: 

1.  The  product  demands  frequent  and  thorough  in- 

spection, as  when  great  accuracy  is  required. 

2.  When  models  are  changed  with  frequency,  as  in  a 

swiftly  advancing  art. 

3.  When  labor  is  unskilled  or  rapidly  changing. 

4.  When  quality  standards  are  being  raised. 

5.  When  considerable  judgment  must  be  used  because 

standards  are  being  shifted  or  have  not  been  re- 
duced to  a  definitely  measurable  basis. 

Each  of  these  cases  may  apply  separately  but  when  they 
are  cumulative,  as  in  the  case  of  unskilled  labor  working  in 
an  industry  that  is  advancing  swiftly,  the  use  of  a  much 
more  intensive  form  of  inspection  is  indicated. 

On  the  other  hand,  if  the  product  is  highly  standardized 
and  if  the  workers  are  skilled  mechanics  well  acquainted 
with  the  requirements  of  the  work,  then  inspection  may  be 
greatly  reduced.  In  fact,  if  the  work  is  performed  under 
these  conditions  and  on  so  small  a  scale  that  the  manage- 
ment is  able  to  devote  considerable  attention  to  the  details 
of  the  business,  the  need  for  inspection  almost  disappears. 
Cases  of  the  latter  sort  are  very  rare,  however,  and  are  not 
worth  considering  except  as  exemplifying  the  extreme  or 
limiting  situation. 

The  following  examples  have  been  chosen  from  a  number 
of  industries  with  the  idea  of  presenting  in  brief  form  certain 
general  features  of  inspection  methods  which  are  typical. 

Inspection  in  Automobile  Plants 

In  looking  for  a  good  example  of  inspection  as  practiced 
in  its  highest  development,  there  is  no  better  place  to  turn 


174 


THE  CONTROL  OF  QUALITY 


than  to  the  automobile  factories.  The  evolution  of  auto- 
mobile design  and  manufacture  is  one  of  the  great  romances 
of  modern  industry.  For  reasons  that  need  no  mention,  it 
has  made  tremendous  demands  upon  every  department  of 
engineering  science  and  the  technical  arts,  in  order  that 
ways  and  means  for  meeting  its  requirements  might  be  de- 
vised. It  has  made  it  necessary  to  create  a  new  school  of 
machine  tool  design,  to  carry  tool-room  precision  into  the 
ordinary  fabricating  shops,  and  to  install  every  reasonable 
safeguard  for  controlling  quality. 

The  Packard  Inspection  Service 

Inspection  in  the  factory  of  the  Packard  Motor  Car  Com- 
pany l  has  been  developed  to  a  point  that  is  best  illustrated 
by  the  organization  chart  shown  in  Figure  39.  The  chief 


FACTORY 
EXECUTIVE  STAFF 

CHIEF  INSPECTOR 

1 

DIVISION    SUPT 
INSPECTION 

ERATION   SUPT. 

I 

1                                                    1                                                  f 

1 

FOREMAN                                FOREMAN                                  F°JE 
FORUE  INSPECTION               FOUNDRY  INSPECTION             |  riNI*Kl£e 

m*"                                           FOREMAN 
*$0«"AL  |                 INSIDE  INSP6C 

FOREMAN 
T,nu                      ROUGH  STOCK 
INSPECTION 

1 

1 

INSPECTORS                          INSPECTORS                           INSPECTORS                              INSPECTOR 

a                            INSPECTORS 

Figure  39.     Inspection  Organization  Chart — Packard  Motor  Car  Company 

inspector  is  responsible  to  the  factory  executive  staff,  com- 
posed of  the  vice-president  of  manufacturing,  the  factory 
manager,  the  assistant  factory  manager,  and  the  general 

1  The  author  is  indebted  to  D.  G.  Stanbrough,  General  Superintendent  of  the  Packard 
Motor  Car  Company,  for  his  courtesy  in  furnishing  information  relative  to  Packard  inspection 
practice  and  precision  methods. 


INSPECTION  IN  PRACTICE  175 

superintendent.  The  chief  inspector  is  responsible  for 
proper  and  efficient  inspection  throughout  the  inspection 
organization,  in  accordance  with  standards  set  by  the  fac- 
tory management. 

Directly  under  the  chief  inspector  is  an  inspection  super- 
intendent for  each  of  the  main  divisions  of  the  business, 
namely,  carriage,  truck,  and  service.  Each  of  these  divi- 
sions is  further  subdivided  into  three  departments :  outside 
finished  material  inspection,  inside  inspection,  and  rough 
stock  inspection,  with  a  foreman  in  charge  of  each  depart- 
ment to  whom  the  individual  inspectors  report.  In  addi- 
tion, there  is  an  alteration  superintendent,  also  responsible 
to  the  chief  inspector,  whose  duty  is  to  see  that  alterations  in 
the  dimensions  or  in  the  design  of  parts  are  properly  put 
through  in  the  factory  with  the  minimum  of  interference. 

Both  floor-inspection  and  centralized  inspection  are  in 
use.  Large  parts,  such  as  cylinders,  crank  cases,  etc.,  are 
inspected  on  the  floor  near  the  machines,  since  manufac- 
turing facilities  are  so  arranged  as  to  permit  it  conveniently. 
Small  parts,  however,  are  removed  to  the  department  in- 
spection cribs  for  inspection.  When  a  workman  machines 
the  first  piece  on  a  job,  he  is  required  to  submit  it  to  the 
foreman  or  the  job-setter.  If  the  piece  is  done  correctly, 
the  foreman  or  job-setter  OK's  the  workman's  time  slip 
and  he  goes  ahead  with  the  job.  If  the  operation  is  not 
done  correctly,  the  foreman  shows  the  workman  how  to  do 
the  operation,  and  the  time  slip  is  not  signed  until  the  piece 
is  finished  correctly. 

Final  inspection  of  each  individual  piece  is  maintained 
on  the  following  parts:  heat  treated  parts  and  parts  that 
are  held  to  close  limits,  such  as  cylinders,  pistons,  piston- 
pins,  crank  cases,  transmission  parts,  gears,  steering 
knuckles,  etc.  Ordinary  small  parts  such  as  screws,  nuts, 
bolts,  washers,  etc.,  are  subjected  to  a  percentage  inspection. 


176 


THE  CONTROL  OF  QUALITY 


The  disposition  of  rejected  parts  is  rigorously  controlled. 
Reference  to  Figure  40  shows  this  in  detail.  While  the 
production  department  may  be  consulted  by  the  chief  in- 


N9  146099 

DEFE 

DATE 

CTIVE 

DiPI   (OUNDIN 

STOCK  TAG  1 

ON 
OROCR 

PICCC   NO 

inaricici; 

DISPOSITION    OATS 

OR.O.  O.PT. 

RCPAIR 
OROCR 

oe"    OHO°- 

»PPUf   ON    TAO    NO 

OPtR.   0«F. 

DIE   NO. 

QUANTITY   DCFCCTIVC 

NAME 

„. 

SCRA, 

REPAIR 

RCTURN 
R«PLAC< 

OC»CTS 

._„ 

ACCCP 

MOUOH 

r 

ASSCMBLK 

FINISHCO 

FOR    RtPAIR   INSTRUCTIONS  511   BACK   Of    NO.    »   COPT 

REPAIR    ROUTING 

PRIC« 

1 

KXTCNStOP* 

1 

(MPMJM 

Figure  40.     (a)  Inspector's  Tag  Disposing  of  Work  (face) — Packard  Motor 

Car  Company 


INSTRUCTIONS  FOR  REPAIR 

DEPT 

OPERATION 

8 

Figure  40.     (b)  Inspector's  Tag  Disposing  of  Work  (reverse) 

spector,  the  fact  remains  that  no  piece  once  rejected  can  be 
disposed  of  except  in  accordance  with  instructions  issued  by 
the  chief  inspector  in  person. 

The  foregoing  pertains  to  the  methods  of  handling  in- 


INSPECTION  IN  PRACTICE  177 

spection  on  forgings,  castings,  semifinished  and  finished 
pieces.  In  addition  to  this,  there  is  a  metallurgical  and 
chemical  department  for  the  usual  analyses  of  iron  and  steel. 
This  department,  however,  is  separate  from  the  regular  in- 
spection organization  and  is  in  charge  of  the  chief  metal- 
lurgist, who  is  responsible  to  the  factory  executive  staff. 
The  chief  metallurgist  also  prescribes  the  requisite  charac- 
teristics for  heat  treated  parts,  although  the  actual  work  of 
inspection  of  these  parts  is  carried  out  through  the  regular 
inspection  organization. 

Operating  inspection  on  finished  vehicles  is  also  a  sepa- 
rate function  in  charge  of  the  operating  manager  who  is  re- 
sponsible directly  to  the  president. 

In  addition  to  all  of  the  above,  the  quality  of  the  product 
is  further  insured  by  a  supervisor  of  quality  (reporting  to 
the  factory  executive  staff)  whose  function  is  to  check  the 
work  of  the  inspection  organization.  The  method  of  the 
supervisor  of  quality  is  to  have  his  men  take  a  complete 
unit  at  random,  which  is  then  disassembled  and  checked  up 
in  detail  by  his  men. 

Inspectors  are  paid  day  work,  which  is  the  almost  uni- 
versal practice.  With  a  working  force  of  9,000  men,  500 
inspectors  were  employed.  It  should  be  noted,  however,  in 
connection  with  any  data  of  this  sort,  that  the  proportion  of 
workers  must  vary  considerably  from  time  to  time,  depend- 
ing upon  the  situation  of  the  work  and  the  number  of  work- 
men employed.  Consequently,  the  figures  that  are  given 
relative  to  the  number  of  inspectors  for  any  given  working 
force  must  be  considered  as  applying  merely  to  a  particular 
situation. 

In  its  general  features  the  above  outline  is  believed  to  be 
typical  of  the  best  automobile  inspection  practice,  although 
there  are  naturally  a  number  of  variations  from  factory  to 
factory.  The  proportion  of  workers  to  inspectors,  for  ex- 

12 


178  THE  CONTROL  OF  QUALITY 

ample,  varies  all  the  way  from  I  inspector  to  10  workers,  up 
to  I  inspector  to  30  workers. 

An  Example  of  Former  Practice 

By  way  of  contrast  with  the  above,  it  may  be  of  interest 
to  compare  the  inspection  methods  in  use  several  years  ago 
in  a  plant  which  at  that  time  was  fairly  prominent  as  the 
maker  of  a  high-grade  car.  In  this  factory  the  chief  inspec- 
tor reported  to  the  chief  engineer  in  matters  affecting  ma- 
terial organization  and  the  holding  of  the  work  to  drawing 
dimensions.  He  was  responsible  to  the  superintendent  for 
the  routing  and  movement  of  all  work  in  process. 

The  inspection  department  organization  consisted  of  a 
chief  inspector,  an  assistant  chief  inspector,  department- 
inspectors,  floor-inspectors,  and  inspectors.  The  depart- 
ment-inspector had  charge  of  all  inspection  in  his  depart- 
ment and  was  responsible  for  the  quality  of  the  work  and 
the  discipline  of  his  force.  There  were  in  general  2  floor- 
inspectors  for  every  150  operators  and  their  duty  was  to 
inspect  all  work  in  process  at  least  four  or  five  times  a  day. 
They  were  required  to  check  each  new  set-up  before  work 
could  start,  after  which  the  machine  operator  was  held 
responsible  for  all  defective  work. 

The  floor-inspectors  inspected  and  had  moved  to  the 
various  operations,  all  large  pieces  of  work,  such  as  crank- 
shafts, axles,  radius-rods,  drive-shafts,  and  fly-wheels.  These 
parts  were  moved  into  the  central  inspection  room  only 
when  finished  or  at  the  time  of  being  moved  from  one  de- 
partment to  another,  in  order  to  fix  departmental  responsi- 
bilities. 

Work  requiring  skilled  mechanics,  such  as  grinding 
crank-shafts,  cam-shafts,  cylinders,  pistons,  piston-rings, 
gear-cutting  and  grinding,  boring  of  crank  cases  and  trans- 
mission cases,  was  not  considered  to  require  floor-inspection. 


INSPECTION  IN  PRACTICE 


179 


180  THE  CONTROL  OF  QUALITY 

The  floor-inspectors  were  usually  expert  machinists  receiving 
(prior  to  1914)  about  70  cents  an  hour,  and  as  an  incentive 
were  usually  next  in  line  for  promotion  to  assistant  foreman 
and  foreman. 

The  amount  of  inspection  given  to  each  lot  of  pieces 
depended  upon  the  quality  of  the  lot  as  determined  by  the 
first  few  pieces  inspected.  That  is  to  say,  if  the  first  few 
pieces  were  good,  the  inspector  examined  about  25  per  cent 
of  the  lot.  If  any  were  bad  he  would  then  inspect  the  entire 
lot.  In  each  case  he  then  counted  the  work  and  credited 
the  operator  with  the  number  of  pieces  passed. 

For  a  force  of  1,500  operators  there  were  40  bench- 
inspectors,  8  floor-inspectors,  2  inspectors  for  commercial 
work,  I  inspector  for  forgings  and  castings,  and  I  inspector 
on  the  scleroscope  test.  All  of  these  men  were  paid  on  the 
hourly  basis,  bench  inspectors  receiving  from  50  to  65  cents 
per  hour.  The  drawing  was  the  only  standard  allowed, 
close  dimensions  being  stated  with  the  limits  given  in  detail. 
Limits  of  plus  or  minus  o.oio  inch  were  allowed  on  all  di- 
mensions which  were  stated  in  fractions.  The  standard  of 
finish  was  marked  on  the  drawing  to  denote  the  points  to  be 
finished,  the  allowance  for  grinding  (say  o.oio  inch),  and 
the  surfaces  to  be  disc-ground  or  spot-faced,  and  no  depar- 
ture was  allowed  from  the  above  without  the  written  au- 
thority of  the  chief  inspector.  It  is  of  interest  to  note  that 
the  company,  being  responsible  only  to  themselves  for  their 
standards,  had  permitted  it  to  become  the  accepted  practice 
in  the  shops  to  shift  the  standards  of  workmanship  and  ma- 
terial to  suit  the  urgency  of  the  demand  for  parts,  keeping  in 
mind  the  ability  of  the  assembling  department  to  use  them 
without  increasing  the  cost  too  much — this  from  the  state- 
ment of  the  chief  inspector  to  the  writer. 

In  the  routing  of  work,  in  accordance  with  operation 
sheets  furnished  to  the  inspector,  the  work  was  accompanied 


INSPECTION  IN  PRACTICE  l8l 

by  a  route  card,  or  traveler,  which  stated  the  part  number, 
order  number,  and  quantity.  This  card  moved  with  the 
work  from  raw  material  to  finished  stock.  When  an  opera- 
tor finished  his  operation,  he  took  the  card  to  his  foreman, 
who  then  gave  it  to  the  time-keeper.  The  time-keeper  then 
made  out  an  inspection  ticket  in  triplicate,  keeping  one  copy 
himself.  The  remaining  two  went  to  the  inspection  depart- 
ment where  the  inspector  filled  out  the  quantity  accepted  or 
rejected.  Of  these  two  copies  one  was  sent  to  the  pay  de- 
partment and  the  other  returned  to  the  workman.  The 
inspector  then  made  out  a  card,  ordering  the  material  out 
of  the  inspection  department  and  delivered  by  the  trucker  to 
the  next  operation. 

Machine  Tool  Industry 

In  the  manufacture  of  machine  tools,  the  organization 
and  methods  of  inspection  do  not  differ  widely  from  those 
employed  in  the  best  run  automobile  factories.  As  might 
be  expected,  however,  the  same  degree  of  refinement  has  not 
been  reached,  although  there  is  evidence  that  inspection 
methods  are  being  overhauled  rather  carefully  in  several  of 
the  machine  tool  making  factories,  as  a  result  of  their  experi- 
ence in  the  war.  The  ratio  of  inspectors  to  workers  varies 
all  the  way  from  i  to  30  for  ordinary  machine  tool  work, 
up  to  i  to  15  in  the  case  of  small  tools.  Inspectors  are  paid 
on  an  hourly  basis.  In  many  plants  central  inspection,  floor- 
inspection,  and  first-piece  inspection  are  all  in  use  together. 

The  most  marked  deviation  in  inspection  organization 
is  in  the  relation  of  the  inspection  department  to  the  rest 
of  the  organization.  In  the  Pratt  and  Whitney  Company, 
for  example,  the  chief  inspector  reports  directly  to  the  works 
manager,  but  this  is  by  no  means  the  general  practice  else- 
where in  the  industry.  In  some  factories  the  chief  inspector 
reports  to  the  engineering  department.  In  others  he  re- 


182  THE  CONTROL  OF  QUALITY 

ports  to  the  factory  superintendent.  These  latter  prac- 
tices are  of  interest  as  indicating  the  results  of  an  inherited 
system. 

Small  Precision  Work 

Inspection  methods  have  reached  a  high  development 
in  many  plants  which  are  engaged  in  the  manufacture  of 
small  high-grade  articles.  For  example,  in  the  Elgin  Na- 
tional Watch  Company's  2  plant  the  inspection  work  is  per- 
formed in  a  central  inspection  room  or  space,  generally  set 
off  at  the  end  of  each  department.  Each  piece  produced  is 
submitted  to  100  per  cent  inspection.  Out  of  a  total  work- 
ing force  of  3,500  the  ratio  of  inspectors  to  workers  averages 
i  to  10.  All  inspectors  are  paid  by  the  day.  Each  main 
factory  division  has  its  own  inspection  department  with  a 
chief  inspector  in  general  charge. 

At  the  Weston  Electrical  Instrument  Company's  3  plant 
at  Waverly  Park,  Newark,  central  inspection  is  in  use,  but  is 
reinforced  for  certain  classes  of  work  by  so-called  "floating 
inspectors"  who  move  through  the  various  departments 
where  inspection  at  the  machine  or  at  the  completion  of  the 
process  seems  to  be  advisable.  In  general,  first-piece  in- 
spection is  held  to  be  a  part  of  the  responsibilityof  the  depart- 
ment in  which  the  work  is  done,  and  is  not  covered  by  the 
inspection  department  except  in  special  cases.  Most  of  the 
work  is  arranged  in  departments — the  milling  department, 
the  drilling  department,  etc.,  but  no  work  is  allowed  to  pass 
from  one  department  to  another  without  first  passing 
through  the  hands  of  the  inspection  department. 

The  ratio  of  inspectors  to  workers  averages  about  I  to 
10,  and  inspectors  are  paid  on  an  hourly  basis. 

Every  piece  of  the  completed  product,  that  is  to  say 


2  From  data  furnished  by  DeForest  Hulburd,  second  Vice-President. 

3  Courtesy  of  Edw.  F.  Weston,  second  Vice-President. 


INSPECTION  IN  PRACTICE 


183 


Figure  42.     Inspection  of  Time  Fuse  Parts 
War  work  of  American  Locomotive  Company. 


1 84  THE  CONTROL  OF  QUALITY 

every  instrument,  undergoes  several  final  inspections.  The 
subassemblies  and  parts  used  in  the  production  of  Weston 
instruments  are  subject  to  individual  inspection.  The  only 
exception  is  in  the  matter  of  unimportant  parts  (such  as  or- 
dinary screws)  which  are  inspected  by  sampling. 

The  chief  inspector  is  responsible  directly  to  the  general 
superintendent,  and  is  assisted  by  a  foreman  and  subf ore- 
men,  each  subforeman  controlling  from  3  to  10  inspectors, 
according  to  the  nature  of  the  work. 

General  Machine  Shop  and  Foundry  Practice 

In  industries  whose  work  requires  medium  and  heavy 
foundry  work,  forgings  and  their  machining,  the  inspection 
department  usually  is  more  loosely  organized,  although  in 
highly  standardized  businesses  of  this  sort,  such  as  the  man- 
ufacture of  power  transmission  machinery,  it  is  usual  to  find 
greater  refinements  in  use,  with  a  chief  inspector  reporting 
directly  to  the  management.  Most  of  the  work  is  inspected 
on  the  floor,  as  a  matter  of  necessity,  but  final  inspection  is 
not  infrequently  performed  in  a  separate  department.  In- 
spectors are  paid  universally  on  an  hourly  rate.  The  ratio 
of  inspectors  to  producers  is  as  low  as  I  to  50. 

Special  Cases 

The  inspection  methods  in  use  in  the  manufacture  of  a 
continuous  product,  such  as  paper  or  textiles,  requires  in- 
dividual treatment,  depending  considerably  on  the  grade  of 
the  product.  The  general  principles,  as  set  forth  for  inter- 
changeable manufacturing,  are  the  same,  but  different 
methods  are  necessary.  All  such  work  should  be  regarded 
as  an  assembling  proposition,  with  various  preparatory 
operations  for  the  raw  material  and  with  appropriate  finish- 
ing operations  after  the  materials  have  been  brought  together 
in  the  goods.  Errors  are  bound  to  occur  and  are  almost 


INSPECTION   IN  PRACTICE 


185 


always  worked  into  the  product  in  such  a  way  as  to  defy 
their  correction.  Consequently,  inspection  at  the  sources  of 
greatest  error  has  an  added  value  in  checking  undue  loss. 
Inspectors  of  high  caliber  are  required,  moreover,  because 
apparently  insignificant 
matters  in  the  earlier 
stages  of  manufacture 
are  likely  to  have  a  seri- 
ous effect  upon  later 
processes.  The  in- 
spector thus  requires  a 
wide  knowledge  of  the 
technicalities  of  the 
business  as  a  whole. 

An  interesting  vari- 
ation in  the  method  of 
inspection  is  occasion- 
ally desirable  for  con- 
tinuous processing — if 
the  workman  is  paid  a 
bonus  for  quality  (and 
consequently  knows 
that  the  defective  work 
will  cost  him  money), 
he  automatically  be- 
comes an  inspector  of 
work  performed  on  the 

material  before  it  reaches  him.  In  fact,  it  may  be  a  desir- 
able feature  in  any  such  scheme  of  quality  control  to  re- 
quire each  operator  to  make  a  list  of  the  defects  he  finds 
in  the  work  as  it  reaches  him,  and,  where  practicable,  to 
report  the  same  before  starting  his  own  machine. 

There  is  another  class  of  inspection  work  which  has  not 
been  touched  upon  heretofore  because  of  its  very  special 


Figure  43.     Perch    for    Inspecting   Textile 
Fabrics — The  Shelton  Looms 


1 86  THE  CONTROL  OF  QUALITY 

nature.  It  is  to  be  found  in  places  where  a  volume  of  mail 
orders  are  packed,  and  in  similar  operations  which  are  more 
in  the  nature  of  checking.  For  example,  in  the  Charles- 
William  Stores 4  at  a  time  when  a  force  of  about  500 
girls  was  employed  in  packing  orders  for  shipment,  the 
orders  ran  in  about  the  general  proportion  of  300  freight, 
3,000  express,  and  30,000  parcels  post.  Obviously,  it  was 
necessary  to  have  some  sort  of  check  on  the  packing, 
although  it  was  equally  true  that  the  inspection  of  this 
packing  could  not  be  carried  very  far  without  duplicating 
the  work  of  the  packers.  Satisfactory  results  were  obtained 
by  the  employment  of  30  girls  as  inspectors,  with  a  man- 
ager or  chief  inspector.  Arrangements  were  made  to  carry 
the  parcels  through  the  inspection  department  on  two  36- 
inch  belt  conveyors.  The  inspection  operation  was  per- 
formed by  sampling ;  that  is  to  say,  an  inspector  would  take 
a  package  from  the  belt,  get  the  papers  in  the  case,  and 
check  the  order  as  filled  and  packed. 

Ratio  of  Inspectors  to  Workers 

As  has  been  stated  before,  any  figures  giving  the  num- 
ber of  inspectors  required,  in  proportion  to  the  working 
force,  must  be  accepted  with  reservations  based  upon  condi- 
tions surrounding  the  work  at  the  time.  Consequently, 
such  figures  can  be  used  only  as  a  general  guide.  As  a  mat- 
ter of  convenience,  the  following  table  summarizes  the  data 
assembled  from  a  number  of  industries : 

Ratio  of  Inspectors  to 
Industry  Workers 

Ball  bearings to  4  or  5 

Small  and  very  precise  interchangeable  parts to  8  or  10 

Automobiles,  high-grade  close  work to  10,  up  to  I  to  20 

Simpler  automobile  work to  20,  up  to  I  to  40 

Machine  tools to  15,  up  to  I  to  40 

Foundry  and  general  machine  shop to  50 

4  Under  the  organization  and  methods  developed  by  its  president,  G.  H.  Eiswald, 


CHAPTER  XII 
QUALITY  CONTROL   IN   PRACTICE 

Complexity  of  the  Quality  Problem 

Inspection  is  only  a  part,  although  a  very  important 
part,  of  the  wide  and  important  subject  of  the  control  of 
quality.  As  has  already  been  pointed  out,  an  analysis  of 
successful  industries  will  show  that  these  manufacturing 
activities  comprise  three  essential  branches  or  stages : 

1 .  Planning  or  Engineering — the  determination  in  con- 

siderable detail,  of  what  is  to  be  made  and  how  it 
is  to  be  made,  before  work  is  begun. 

2.  Production — the  economical  application  of  suitable 

manufacturing  processes  whose  output  is  con- 
trollable to  uniform  standards  of  quality. 

3.  Inspection — the  comparison  of  the  work  as  produced 

with  the  predetermined  standards  of  quality,  and 
the  filtering  of  unsatisfactory  work  out  of  the  line 
of  flow  of  work  in  process. 

The  determination  of  what  makes  an  enterprise  success- 
ful is  a  difficult  matter  in  any  case.  Some  things  help, 
others  hinder,  and  some  are  merely  carried  along  without 
affecting  the  issue  either  way.  Not  infrequently  success 
results  from  a  combination  of  circumstances  which  are 
merely  opportune,  and  vice  versa.  The  resulting  mixture  of 
causes  is  so  complex  that  it  is  hard  to  analyze.  If,  however, 
we  approach  the  matter  from  the  negative  viewpoint,  it  is 
simpler  to  determine  what  the  basic  causes  of  success  really 
are.  The  test  in  this  case  is:  What  are  the  things  whose 
non-observance  will  result  in  failure?  As  indicated  above, 

187 


1 88  THE  CONTROL  OF  QUALITY 

it  is  believed  that  a  very  small  oversight  in  any  one  of  the 
three  essential  branches  of  planning,  production,  and  inspec- 
tion may  be  disastrous ;  while  the  same  thing  cannot  be  said 
with  equal  truth  of  the  other  branches  of  factory  endeavor. 

By  the  above  test  then,  we  should  expect  to  find  un- 
usually successful  industrial  enterprises  accompanied  by  a 
close  attention  to  planning,  production,  and  inspection. 
The  war  furnished  a  number  of  examples  which  illustrate 
the  above  in  a  conspicuous  way,  both  by  direct  and  by  nega- 
tive proof.  Unfortunately,  however,  everybody  was  so 
busy  at  the  time  that  the  most  valuable  lessons  to  be  gained 
from  war  time  experience  were  missed,  except  by  the  people 
who  came  in  actual  contact  with  the  industries  in  question. 
This  is  doubly  unfortunate  because  the  conditions  were 
especially  good  for  proving  in  a  very  intensive  way  the 
truth  or  untruth  of  the  methods  used. 

It  is,  of  course,  difficult  to  choose  typical  examples  from 
such  a  quantity  as  are  available,  but  the  war  work  of  the 
American  Locomotive  Company,  the  Lincoln  Motor  Com- 
pany, and  the  Remington  Arms  of  Delaware  may  be  selec- 
ted as  illustrating  strikingly  the  points  made  throughout 
this  book. 

The  Shell  Contracts  of  the  American  Locomotive  Company 

Early  in  1915,  the  American  Locomotive  Company 
undertook  the  manufacture  of  shrapnel  and  high  explosive 
shells  for  the  British  government.  The  work  was  carried 
on  under  the  direction  of  Vice- President  C.  K.  Lassiter  (in 
charge  of  manufacturing).  The  excellence  and  importance 
of  this  accomplishment  are  not  generally  known.  Such 
results,  however,  might  have  been  expected  of  one  who 
already  had  an  enviable  record  as  a  designer  of  highly  effi- 
cient machine  tools,  and  as  a  production  executive.  As  will 
be  observed  from  the  accompanying  illustrations,  Mr.  Las- 


QUALITY  CONTROL  IN  PRACTICE  189 

siter's  methods  are  characterized  by  directness,  simplicity, 
and  effectiveness — in  short,  by  that  absence  of  frills  which 
denotes  a  genius  for  making  things. 

In  order  that  the  magnitude  of  the  undertaking  may  be 
appreciated  (for  it  shortly  grew  to  huge  proportions),  the 
following  summary  of  the  work  done  by  the  American  Lo- 
comotive Company  and  its  associated  shops  is  of  interest : 

Manufactured  complete,  loaded  3-3-in.  Shrapnel.   2,500,000 


3-3 
not  loaded  4 . 5 

«       «       6 


9.2 

Extra  cartridge  cases,  complete    3 . 3 

4-5 


H.  E 2,500,000 

H.  E 1,468,000 

H.  E 1,468,000 

H.E 300,000 

H.  E 125,000 

3,886,000 

1,147,000 


time  fuses,  complete,  loaded 3,200,000 

"     shell  forgings — various  sizes 2,733,700 

During  the  last  nine  months  of  the  undertaking  this  tidy 
little  job  reached  an  average  total  daily  output  of  25,000  tons, 
and  employed  40,000  men.  The  average  daily  output  of 
cartridge  cases  alone  was  58,000;  while  of  3.3-inch  shrapnel 
and  H.  E.  shells  it  was  40,000.  To  accomplish  these  results 
with  an  organization  unacquainted  with  the  work,  however 
skilled  it  might  be  in  other  lines,  certainly  would  indicate  a 
thorough  grasp  of  the  fundamentals  of  manufacturing. 

Beginning  the  Work 

The  first  order  undertaken  was  for  1,250,000  3.3-inch 
1 8  pdr.  shrapnel,  and  a  like  number  of  3.3-inch  high  explo- 
sive shell.  Not  one  of  these  was  rejected  after  delivery.  Let 
us  now  see  how  the  thing  was  done,  beginning  with  the  car- 
tridge case,  which  is  the  same  for  both  shrapnel  and  H.  E. 
shell. 

At  the  outset  it  should  be  noted  that  the  contract  pro- 
vided only  an  outline  plan  without  tolerances  or  limits. 
The  first  step  took  the  form  of  a  visit  to  the  Quebec  Arsenal, 


190  THE  CONTROL  OF  QUALITY 

where  inquiries  were  made  as  to  what  these  cases  should  be 
like.  In  other  words,  Mr.  Lassiter  first  endeavored  to  de- 
termine what  was  wanted,  in  detail ;  in  fact,  he  frankly  stated 
that  he  and  his  associates  approached  the  work  as  novices. 
As  a  special  result  of  this  visit,  two  sample  cartridge  cases 
which  were  satisfactory  were  obtained  and  brought  back  to 
New  York.  These  samples  were  then  sawed  in  two,  and  the 
hardness  determined  by  careful  and  extended  measurements 
with  the  scleroscope.  Dies  were  designed  and  a  set  of  tools 
made  to  produce  the  case  from  blank  to  finish,  special  atten- 
tion being  paid  to  see  that  the  drawing  processes  were  de- 
veloped to  secure  the  necessary  coining  at  the  points  where 
extra  hardness  was  required.  Tolerances  and  limits  were 
then  worked  out. 

As  an  example  of  the  processing,  the  annealing  furnaces 
were  of  the  oil,  overfired,  perforated  roof  type.  In  order  to 
avoid  scale,  superheated  steam  was  introduced,  at  a  suffi- 
ciently high  temperature  to  permit  uniform  control. 

Limit  gages  and  100  per  cent  inspection  were  provided 
for  all  operations  from  rough  blanks  to  finished  cases.  All 
work  rejected  by  either  the  company  or  the  purchaser's  in- 
spection was  forthwith  removed  from  the  line  of  flow  and 
sent  to  a  hospital.  Needless  to  say,  the  latter  was  pretty 
large  at  times ;  but  this  practice  permitted  an  unbroken  flow 
of  work  from  operation  to  operation.  The  value  of  this 
practice  was  enhanced  by  the  excellent  handling  devices 
and  conveyors,  which  were  provided  everywhere  throughout 
the  shops. 

No  Rejections  After  Delivery 

The  plant  for  this  work  was  laid  out  for  an  output  of 
9,000  per  day  of  20  hours,  but  the  actual  output  reached 
was  24,000.  The  quality  of  the  first  series  submitted  to  the 
purchaser  was  highly  commended,  even  after  firing  some  of 


QUALITY  CONTROL  IN  PRACTICE  IQI 

the  cases  three  times.  Not  one  series  nor  one  single  case 
out  of  the  2,500,000  was  rejected  after  delivery;  and  the 
same  statement  holds  for  the  complete  and  loaded  shells. 

Mr.  Lassiter,  in  speaking  of  this  part  of  the  work,  recently 
said,  "We  were  novices,  so  the  first  thing  we  had  to  do  was 
to  find  out  what  we  had  to  make,  then  we  had  to  make  all 
our  processes  alike,  and  finally  we  had  to  inspect  everything." 

To  what  extent  the  first  thing  was  done,  is  shown  very 
clearly  by  the  little  yH  by  3%  inch  booklets  which  were 
supplied  to  the  shops.  Each  booklet  contains  an  index  and 
about  40  pages  of  blue  prints,  which  give  all  the  necessary 
information  as  to  the  product,  the  tools  for  making  it,  the 
shop  arrangement,  and  so  on.  Sample  pages  are  shown  in 
Figure  44.  In  connection  with  the  simple  but  complete 
way  in  which  similar  information  was  developed,  attention 
is  invited  to  Figures  45  and  46.  They  contain  no  unneces- 
sary information,  yet  everything  needed  is  there. 

Shells 

The  importance  of  getting  processes  under  uniform  con- 
trol is  illustrated  even  better  by  some  of  the  difficulties 
encountered  in  making  the  shrapnel  and  H.  E.  shells.  In 
general  terms,  the  usual  processing  in  the  early  stages  is  to 
forge,  rough  turn,  harden,  and  grind  to  finish.  It  was  de- 
sired to  substitute  finish  turning  for  grinding,  in  order  to 
get  greater  production.  The  problem  was  to  get  them  soft 
enough  to  turn,  but  hard  enough  to  meet  the  ballistic  re- 
quirements without  the  walls  of  the  shell  upsetting  in  firing. 
This,  of  course,  involves  very  uniform  heat  treatment. 

A  furnace  was  built  24  feet  long,  with  six  pyrometers 
spaced  along  the  sides.  The  shells  were  placed  in  special 
triple  pocket  cradles,  and  were  pushed  into  one  end  of  the 
furnace  by  a  pneumatic  pusher.  The  pyrometer  at  the 
entrance  fluctuated,  but  the  sixth  pyrometer  was  steady, 


SHELL  Q.F.  18  POUNDER  SHRAPNEL 
MARK  IX/L/ 


H3.66 


L3.64" 

H  3.31" 
L3.29"1 


MM 


Total  Pressure  =150  tons 
Pressure  per  sq.  in.  «=  33,500  Ibs. 
Gauge  Pressure  «=-1500  Ibs.  max. 
(Area  of  band  after  compression) 


DRIVING  BAND 
R.L.  13413  A. 


Figure  44.     (a)  Typical  Page  from  Shop  Instruction  Book 
American  Locomotive  Company  practice. 


192 


SOCKET 

_LH  2.515^JL  2.1 
-H  2,425^-L  2.4 


14  Thds. 
per  Inch 
R.H. 


CENTRAL  TUBE 
s-.08"Class  "C"  Metal  or  Mild  Steel 


Chamfer         *fl  Thds.  per  Inch  R.H. 


Figure  44.     (b)  Typical  Page  from  Shop  Instruction  Book 
13  193 


MATERIAL  STEEL  CARBON  70%  OR  OVER 
FINISH  ALL  OVER 


PUNCH   FOR 
DRAWING  OPERATION 


PUNCH   FOR 
PIERCING  OPERATION 


|<— ln/w- 


Figure  44.     (c)  Typical  Page  from  Shop  Instruction  Book 
194 


MAP  OF  PRESSES  IN 

Tapering-4,5"     2nd  Tapering-18*        CARTRIDGE  SHOP 


(Toledo*  17 
style*ll* 


3rd  Tapering-18*    1st  Tapertng-18*    Heading  Press-18* 


Flash 
Anneal 
urnace 


Rack  Press 


Rack  Press 


Bliss 
Trim- 
mer 

Bliss  *5 

Toledo  *9 
Style*857 

Crank  Press 


Rack  Press 


Rack  Press 


Crank  Press 


Crank  Press 


Trim- 
mer 


1  Bliss  *8     1 
1  Style  *78^2[ 

Crank  Press 


Crank  Press 

1  Bliss*!     1 
|style*77^[ 

Crank  Press 


Toledo  *5 

Style  *857 


Rack  Press 


Crank  Press 


Crank  Press 


Figure  44.     (d)  Typical  Page  from  Shop  Instruction  Book 

195 


No.  6.  7-0"ciearance 
200  Ton 
L6(Centers 
5'Posts 


No.  7.  7-0  Clearance 

360  Ton 

6V2"&  6'Centers 

GVa'Posts 


No.  5.  7-'o'  Clearance 
200  Ton 

6y*'&  6'Centera 
6  Posts 


No.  8.  7-0  Clearance 
350  Ton, 
6V"&  6  Centers 
61/-' Posts 


No.  9.  7-0  Clearance 

350  Ton, 

6V2-&  6  Centers 

GVsPosts 


No.  4.  6-3  Clearance 
3^0  Ton 
^..Centers 
7  Posts 


No.  2.  7-6  Clearance 
200  Ton 

'&  6"Centers 
5Tosts 


No.  10.  7-0"Clearance 
200  Ton 

iters 
Posts 


No.  2.  7-8  Clearance 

2$5  Ton 

7  Slots,  4?/2  Centers 

5Vil'Posts 


No.  U.  6-'3Clearance 

350  Ton 

e'Cenfte 

•/Posts 


No.  1.  5-0  Clearance 

350  Ton 

6W&  6  Centers 

6^1'Posts 


Figure  44.     (e)  Typical  Page  from  Shop  Instruction  Book 
196 


QUALITY  CONTROL  IN  PRACTICE  197 

showing  that  the  furnace  was  long  enough  to  permit  equilib- 
rium to  be  reached.  Presently  it  became  possible  to  adjust 
the  temperature  to  suit  the  various  "heats"  of  steel. 

The  furnace  unloaded  automatically  through  a  low  door 
and  into  a  cooling  oil  tank,  which  was  equipped  with  an 
elevator.  As  it  soon  developed  that  this  cooling  tank  did 
not  provide  constant  conditions,  a  lo-ton  refrigerating 
plant  was  installed ;  also  two  circulating  pumps  to  keep  the 
oil  bath  uniformly  mixed.  A  similar  furnace  equipment 
was  used  to  draw  out  the  hard  spots,  which  were  found  to 
occur  from  time  to  time  if  only  the  heat  treating  furnace  was 
used.  After  heat  treatment  and  annealing,  all  shells  were 
scleroscoped. 

As  a  result  of  this  process  it  was  possible  to  substitute 
finish  turning  with  a  very  fine  feed,  instead  of  grinding,  with 
a  resultant  saving  of  50  per  cent  in  cost,  no  loss  ballistically, 
and  no  loss  from  failure  to  clean  up  in  turning.  The  loss 
from  the  latter  cause,  by  the  method  previously  used,  had 
run  as  high  as  20  per  cent  at  times. 

Bullets 

The  first  difficulty  encountered  was  to  get  the  required 
amount  of  antimony  into  the  lead,  and  in  a  uniform  mixture. 
This  was  met  by  adding  the  antimony  in  progressive  steps, 
one-fourth  being  put  into  the  lead  at  each  melting.  The 
metal  was  then  extruded  into  ^-inch  wire  and  wound  on 
reels.  Each  bullet  press  used  16  reels,  and  operated  at  90 
strokes  per  minute. 

The  little  fins  left  by  the  press  were  tumbled  off  in  slat 
rumblers.  Naturally  some  bullets  got  too  much  tumbling 
and  ran  out  of  round.  As  the  elimination  of  the  latter  by 
means  of  the  usual  bean-sorting  belt  was  deemed  to  be  too 
slow  and  costly,  a  simple,  inclined,  gravity,  separation  table 
was  provided.  The  bullets  were  allowed  to  roll  down  this 


198 


THE  CONTROL  OF  QUALITY 


QUALITY  CONTROL  IN  PRACTICE 


199 


© 


2! 
Is 


li 

M! 


Pi 


it. 


1 53 


200  THE  CONTROL  OF  QUALITY 

table  and  thus  classify  themselves  automatically,  as  regards 
their  lack  of  sphericity. 

By  such  methods  as  those  just  related  a  supply  of  bul- 
lets of  the  required  hardness  and  roundness  was  soon  ob- 
tained. The  plant  requirements  were  60  tons  per  day,  but 
they  were  soon  able  to  supply  other  plants  which  had 
encountered  trouble  in  making  bullets. 

Time  Fuses 

Everyone  knows  of  the  grief  encountered  in  making  and 
loading  time  fuses,  so  that  a  mere  statement  that  the  Ameri- 
can Locomotive  Company  produced  millions  of  them  suc- 
cessfully, with  no  explosions  or  injuries  to  employees,  should 
be  indicative  of  the  care  that  was  taken.  They  had  to  find 
out  that  no  two  lots  of  powder  are  sufficiently  alike  to  per- 
mit loading  for  a  uniform  burning  time  of  21  seconds + or  — 
0.2  second.  They  started  without  any  knowledge  of  the 
business  and  had  to  feel  their  way.  But  they  did  know  the 
principles  which  must  be  followed  in  making  anything. 

They  developed  a  simple  type  of  powder  blender  and 
created  a  larger  supply  of  uniform  powder.  Then  they 
learned  that  powder  will  not  pack  to  burn  accurately  unless 
the  humidity  of  the  air  is  constant,  so  the  air  for  the  loading 
rooms  was  first  dried  by  freezing,  and  then  conditioned  to  a 
standard  humidity.  In  order  to  make  sure  of  the  ±0.2- 
second  limits  in  burning  time,  they  paralleled  the  com- 
mercial type  of  chronographic  instrument  with  a  time- 
measuring  instrument  of  their  own  design. 

The  following  item  is  significant :  The  second  lot  of  fuses 
went  wrong  in  burning  time,  and  the  trouble  was  located 
promptly  as  occurring  in  one  of  the  17  separate  loading  sta- 
tions. There  were  seven  men  in  that  room  instead  of  the 
usual  five.  In  the  hot  weather  this  caused  sufficient  varia- 
tions in  humidity  to  affect  the  firing  time.  Would  it  have 


QUALITY  CONTROL  IN  PRACTICE  2OI 

been  possible  to  locate  such  a  difficulty  promptly  without 
an  efficiently  handled  inspection  service? 

Quality  First — Then  Quantity  Follows 

Mr.  Lassiter  believes  in  inspection,  just  as  he  knows  that 
the  first  move  toward  quantity  production  is  to  make  things 
right.  In  this  work  the  ratio  of  inspectors  was  i  to  every  4 
workmen. 

The  percentage  of  work  rejected  in  process  inspection 
varied  widely  from  time  to  time,  as  must  always  be  the  case. 
When  the  estimates  were  made  for  submitting  proposals  for 
the  contracts,  a  5  per  cent  loss  in  manufacture  was  allowed 
for.  When  starting  on  production,  the  inspectors  were  very 
rigid  and  the  temporary  rejections  amounted  to  about  19  per 
cent.  These  rejections  were  held  in  suspense,  however, 
until  a  hospital  could  be  organized  for  reclaiming  some  of 
the  product.  This  was  done,  as  already  stated,  so  that 
rejections  could  not  stop  the  progress  of  the  flow  of  work 
through  the  machines.  As  the  work  progressed  and  the 
organization  learned  more  about  the  business,  rejections 
began  gradually  to  decrease,  so  that  upon  the  completion 
of  the  job  it  was  found  that  the  total  losses  from  every 
cause  in  the  process  of  manufacturing  was  only  6  per  cent. 
The  total  loss  therefore  exceeded  the  estimated  loss  by  I  per 
cent,  but  the  reduction  in  cost  below  the  estimated  cost 
greatly  exceeded  the  I  per  cent  excess  of  loss. 

Mr.  Lassiter  states: 

If  we  had  not  provided  our  enormous  staff  of  inspectors,  who 
checked  each  operation  on  the  work  as  it  progressed  through  the 
shops,  with  limit  gages  with  very  close  tolerances  our  loss  would 
have  run  into  an  enormous  sum  of  money.  Therefore,  one  of  the 
causes  of  our  great  success  in  the  economical  manufacture  of 
shells  was  our  large  staff  of  inspectors,  the  tolerances  which  we 
established  on  the  limit  gages  and  the  system  which  we  installed. 


202 


THE  CONTROL  OF  QUALITY 


- 

*  1 


QUALITY  CONTROL  IN  PRACTICE  203 

It  is  to  be  regretted  that  the  very  many  other  interesting 
features  of  this  work  cannot  be  presented  here.  The  meth- 
ods pursued,  as  shown  by  the  salient  features  already  men- 
tioned, strikingly  illustrate  the  premises  laid  down  at  the 
beginning  of  the  chapter. 

Liberty  Motors  at  the  Lincoln  Motor  Company1 

The  name  of  Leland  has  long  been  associated  with  the 
idea  of  precision  and  fine  workmanship  carried  to  the  nth 
degree.  Henry  M.  Leland  began  his  career  in  the  Spring- 
field Arsenal,  and  later  extended  his  experience  from  firearms 
into  the  field  of  manufacturing  sewing  machines  and  ma- 
chine tools.  With  his  son,  Wilfred  C.  Leland,  he  was  one  of 
the  pioneers  of  the  motor  car  industry.  Together  they 
carried  the  Cadillac  factory  to  a  point  where  hundreds  of 
machine  operations  were  held  within  0.0005  inch  of  the 
absolute  dimensions. 

In  1917,  they  established  the  Lincoln  Motor  Company 
to  build  Liberty  engines  for  the  United  States  Air  Service. 
The  first  contract,  dated  August  31,  1917,  was  for  6,000 
engines,  and  contemplated  an  ultimate  output  of  70 
1 2 -cylinder  engines  a  day.  Henry  M.  Leland,  then  74 
years  old,  made  this  pledge  to  General  Squier: 

It's  true  that  we  have  no  factory  now.  But  we  have  the  know- 
how.  We  will  guarantee  to  build  within  a  specified  time  as  many 
motors  and  of  at  least  as  good  quality  as  will  be  produced  in  any 
existing  plant. 

The  land  was  acquired  and  an  $8,000,000  plant  built  and 
equipped.  This  called  for  over  90,000  special  tools,  among 
which  were  6,522  separate  designs.  Mr.  Leland  told  the 
writer  that  the  large  number  of  tools  and  gages  as  well  as  the 
time  required  to  get  started  was  questioned  by  some  of  the 

1  The  statements  made  are  taken  from  "A  Pledge  Made  Good  by  Deeds,"  published  in 
the  Detroit  Free  Press,  and  are  supplemented  by  data  obtained  by  the  author  in  conversation  with 
Henry  M.  Leland  during  a  visit  to  the  Lincoln  Motor  Company's  factory. 


204 


THE  CONTROL  OF  QUALITY 


9-17-20        4  Sheets, 

Sheet  No.  i 

LINCOLN    MOTOR    COMPANY 

OPERATION  SHEET 

PART  NAME:              HOUSING  FOR  TRANS.  CONTROL  LEVER                   PA^T  No.  2002 

Kind  of 

Machine, 

Machine  Size, 

Oper. 

Name  of 

Dept. 

No. 

&  Special  Tools 

Tool 

No. 

Commercial 

No. 

Operation 

No. 

Req'd 

Per  Set  Up 

No. 

Req'd 

Tools  Per  Set  Up 

L.   M.    Co. 

Mach.  No. 

5 

Inspect 

M-I9 

Bench 

i 

Gauge  for  check- 

ing   depth  of 

core  from  un- 

finished    face 

of  boss  5  1/2 

dia. 

11948 

10 

Snag 

K-i6 

12 

Inspect 

M-36 

Bench 

13 

Sand  blast 

K-i7 

IS 

Rough  and  fin- 

K-23 

#6W&S  Screw 

ish  bore, 

Machine 

1965 

i 

i  o"    Face    plate 

rough  tap 

i 

Face   plate   fix- 

(Std.   W    &    S) 

large  hole 

ture  and  lay- 

#i96-A 

and  rough 

out 

4128 

i 

i  3/4-i6  Go  thd. 

and  finish 

i 

Tool   block   for 

gage  Go  &  No 

face  base 

rough  and  fin- 

Go 

ish  facing 

base 

4135 

i 

1.686     Go     plug 

gage  with 

handle 

i 

i.  690  No  Go  plug 

2 

Bar  for  roughing 

gage  handle 

and   finishing 

i 

i.  654  Go  plug 

inside  dia.and 

gage  with 

thread  dia. 

4U6 

i 

i.  656  No  Go  plug 

gage  handle 

I 

Gauge  for   set- 

3 

#641    Warner    & 

ting     cutters 

Swasey     flanged 

on  finish  bor- 

tool holder 

ing  bar 

4138 

i 

Shell  reamer 

I 

Alignment    bar 

1.655  dia. 

for     i  1/4-1- 

i 

Holder  for  shell 

3/8-i.6s4and 

reamer  #8  Std. 

i.  686  holes 

Tool  Co. 

with  stop  col- 

lar for  testing 

i 

Floating  tool 

squareness  of 

holder  W  &  S 

base 

4506 

I 

#M-652 

Figure  48.     Typical  Operation  Sheet — Lincoln  Motor  Company 


QUALITY  CONTROL  IN  PRACTICE  205 

M-i6  Part  2002 

HOUSING  FOR  TRANSMISSION   CONTROL  LEVER 

1 .  Observe  for  burrs,  cracks,  sandholes  and  other  casting  defects,  also 
that  radii,  chamfers  and  countersinks  are  as  per  Blue  Print. 

2.  Observe  four  13/32  drilled  holes  and  3/4  dia.  counterbore. 

3.  Check  8"  over  all  height  with  Template  Tool  #4512. 

4.  Check  10-24  threaded  hole  with  Go  and  No  Go  Plug  Thread  Guages. 
The  "Go"  end  of  guage  must  enter  to  the  depth  as  shown  on 
drawing.     Threads  may  be  passed  as  O.K.  if  they  are  a  snug  fit  on 
"No  Go"  end  of  gauge. 

5.  Check  1-3/4—16  threaded  hole  with  Plug  Thread  Gauges.     The  Go 
end  of  gauge  must  enter  to  a  depth  of  1/2"  as  shown  on  drawing. 
Threads  may  be  passed  as  O.K.  if  they  are  a  snug  fit  on  No  Go 
gauge. 

6.  Check  .999-1.001  reamed  hole  with  Plug  Gauge. 

7.  Check  1.654-1.656  diameter  bore  with  Plug  Gauges. 

8.  Check  .1 865/^75  diameter  reamed  hole  with  Plug  Gauge. 

9.  Check  .248/.25O  hole  with  Plug  Gauge  Tool  #4514. 

10.  Check  .748/.75O  diameter  reamed  hole  with  "Go"  and  alignment 
Plug  Tool  #4915,  also  with  "No  Go"  Plug  Gauge. 

11.  Check  alignment  of  .248/.25O  and  .999-1.001  holes  with  Tool  #4508. 

12.  Check  1-5/64  counterbore  depth  and  diameter  with  Template  Tool 
#45H. 

13.  Check  depth  of  3/8  diameter  of  counterbore  with  Tool  #4920. 

14.  Check  3/8"  thickness  of  bosses  with  Tool  Snap  Gauge  .365-.3S5. 

15.  Check  7/8"  dimension  faces  of  bosses  with  Snap  Gauge  Tool  #4509. 

1 6.  Check  angle  and  radius  on  top  with  Tool  #4707. 

17.  Check  .3O7-.3I7  dimension  with  Tool  #4919. 

1 8.  Check  1-5/8  dimension  with  Tool  #4921. 

19.  Check  1.810/1.820  dimension  with  Bar  Gauge,  Tool  #4513. 

20.  Check  1.624/1.630  dimension  face  of  bosses  with  Bar  Gauge  Tool 
#5440. 

21.  Check  7-1/2  dimension,  6-9/16  dimension  and  5-7/8  dimension  for 
location  in  relation  to  1-1/4  DOre  with  Tools  #10540-10541  &  10542. 

22.  Check  7-11/16  dimension  depth  of  bore  to  base  with  Tool  #4510. 

23.  Check  alignment  of  1.654/1.656  bore  with  threaded  hole  and  square- 
ness with  base,  the  1.990/2.010  dimension,  the  .9O5/.9IO  dimension 
and  1.148/1.154  dimension,  with  fixture  Tool  #4507. 

24.  Check  the  13/32  depth  of  .248-.25O  hole  with  Tool  #10775. 


Figure  49.  Typical  Instructions  for  Inspection — Lincoln  Motor  Company 


206  THE  CONTROL  OF  QUALITY 

government  inspectors,  but  that  he  considered  it  absolutely 
necessary  to  get  things  right  before  beginning  production. 

The  company  built  up  an  organization  of  6,000  people 
and  produced  2,000  Liberty  motors  within  one  year  of  its 
formation.  Before  the  close  of  1918,  it  produced  the  largest 
number  of  motors  in  a  single  day,  the  largest  number  in  a 
single  month,  and  the  largest  total  rolled  up  by  any  manu- 
facturer. It  completed  its  final  contract  16  days  ahead  of 
schedule,  and  received  the  highest  commendation  for  its 
motors. 

It  is  stated  that  the  leading  English  manufacturer,  with 
j  years  of  aircraft  engine  experience  and  10,000  employees, 
was  producing  at  the  rate  of  50  motors  per  week.  With  this 
for  a  background,  it  is  easier  to  measure  the  achievement  of 
the  Lelands,  for  the  Lincoln  Motor  Company,  with  6,000 
employees  and  after  only  i  year's  development,  was  pro- 
ducing at  the  rate  of  50  motors  per  day. 

Mr.  Leland  has  always  been  guided  by  a  desire  to  do 
things  right.  Quality  is  his  hobby  and  he  carries  it  to  the 
point  of  gathering  his  men  together  in  little  groups  in  the 
shops  and  talking  quality  to  them.  Furthermore,  he  knows 
the  precision  that  is  necessary  for  such  work  and  how  to  get 
it,  as  is  evident  to  anyone  who  has  the  privilege  of  going 
through  the  shops  of  the  Lincoln  Motor  Company.  The 
shops  show  it  in  their  equipment  and  management.  What 
is  more  important,  the  work  in  process  shows  it.  Several 
illustrations  which  bear  this  out  are  to  be  found  throughout 
this  book,  where  they  have  been  placed  to  exemplify  certain 
methods.  In  particular,  attention  is  invited  to  Figures  6, 
8,  12,  15,  48,  49,  and  64. 

Remington  Arms  Company — Springfield-Enfield  Rifle  Production 

Our  armies  in  the  field  never  lacked  American-made 

small-arms  and  small-arms  ammunition,  a  statement  that 


QUALITY  CONTROL  IN  PRACTICE  207 

hardly  holds  for  any  other  of  their  arms  equipment.  More 
than  to  any  other  one  man,  the  credit  for  this  fact  is  due  to 
the  war  time  Director  of  Arsenals,  Brigadier-General  John  T. 
Thompson,  U.  S.  A.  (Retired),  D.  S.  M.  He  developed  the 
war  plans  of  the  Army  Ordnance  Department  as  a  result  of 
personal  experience  in  the  Spanish-American  War,  and  had 
charge  of  developing  the  Springfield  rifle,  thus  gaining 
recognition  internationally  as  a  small-arms  expert.  More 
recently,  in  association  with  his  son,  Colonel  M.  H.  Thomp- 
son, he  has  brought  out  that  remarkable  arm  known  as  the 
Thompson  sub-machine  gun. 

I  Jj  In  September  of  1914,  he  told  the  writer  one  afternoon, 
on  the  front  steps  of  the  State,  War  and  Navy  Department 
building  in  Washington : 

We  are  going  to  be  forced  into  this  war  sooner  or  later.  I  am 
going  into  civil  life  (he  had  just  re  tired  as  a  colonel)  to  help  teach  our 
people  how  to  make  military  rifles  and  rifle-making  machinery. 
There  are  not  nearly  enough  military  rifles  in  the  world.  This 
country  will  be  flooded  with  foreign  orders,  and  these  orders  can 
be  used  to  get  the  private  armories  ready  to  meet  our  own  needs 
later  on.  All  our  military  rifles  have  been  made  heretofore  at 
Springfield  or  Rock  Island  in  government  plants  only :  and  making 
sporting  rifles  is  not  the  same  thing  as  making  millions  of  military 
small-arms  exactly  alike. 

So  General  Thompson  joined  the  staff  of  the  Remington 
Arms  Company,  where  he  laid  the  plans  for  the  huge  armories 
at  Bridgeport  and  Eddystone.  Subsequently  he  went  to 
the  Eddystone  plant  (the  Remington  Arms  Company  of 
Delaware)  and  acted  as  consulting  engineer  during  the 
manufacture  of  Enfield  rifles  for  the  British  government. 
When  the  United  States  entered  the  war  he  was  recalled  to 
Washington  to  take  charge  of  the  production  of  small-arms 
and  their  ammunition. 

Some  time  later  came  the  so-called  "broomstick"  in- 
vestigation by  Congress,  following  the  tardy  discovery 


208  THE  CONTROL  OF  QUALITY 

that  this  country  did  not  have  rifles  enough  to  arm  our 
troops.  Of  course  we  did  not.  Congress  had  never  given 
us  a  chance  to  have  them.  To  those  most  interested  tech- 
nically, the  outstanding  feature  of  the  investigation  was  the 
discussion  of  tolerances.  Many  of  the  private  manufac- 
turers wanted  tolerances  and  limits  increased — "to  get 
greater  production."  General  Thompson  insisted  that  the 
contrary  was  true,  and  that  even  closer  limits  would  result 
in  greater  production  as  well  as  in  better  arms.  Not  only 
that,  but  he  had  the  courage  to  insist  on  converting  the 
Enfield  rifle  to  use  the  better  Springfield  cartridge ;  hence  the 
Springfield-Enfield.  This  meant  that  14  parts  had  to  be 
changed,  and  the  necessary  delay  in  changing  tools  and 
gages  had  to  be  accepted.  As  a  further  step  toward  greater 
precision,  also  at  the  expense  of  time  at  the  start,  the  gages 
of  the  different  armories  and  arms  factories  were  brought 
into  accurate  agreement.  Was  the  General  correct  in  his 
contention  that  quality  preceded  quantity  production? 
Let  the  facts  speak  for  themselves. 

In  the  first  place,  rifles  were  ready  for  all  troops  at  least 
by  the  time  they  sailed  for  Europe ;  and  they  never  lacked 
them  in  the  field.  Several  plants  were  engaged  in  making 
these  arms,  but  the  greatest  output  was  delivered  by  the 
Eddystone  armory,  where  the  daily  output  reached  the  re- 
markable total  of  5,000.  More  interesting  still,  the  number 
of  rifles  finally  assembled  per  man  per  day  started  at  40 
(which  according  to  the  best  data  available,  was  formerly 
considered  a  good  figure  for  this  rifle),  then  increased  to  120, 
and  finally  reached  a  figure  of  160.  As  to  the  quality  of  the 
American  rifles  thus  produced,  for  this  was  undoubtedly  a 
factor  in  the  fine  shooting  of  our  troops  in  the  field,  let  the 
Germans  before  Chateau-Thierry  (and  elsewhere)  tell  the 
story.  According  to  report,  they  repeatedly  mistook  rifle 
fire  for  machine  guns  and  shrapnel. 


QUALITY  CONTROL  IN  PRACTICE  209 

Quality  Is  the  Road  to  Production 

To  summarize:  Mr.  Lassiter  developed  an  organization 
of  40,000  men  and  produced  25,000  tons  of  munitions  per 
day  with  only  6  per  cent  of  spoilage;  Mr.  Leland  started 
with  not  even  the  land  for  a  factory,  built  a  plant,  gathered 
6,000  workers  and  produced  2,000  Liberty  motors  to  meet 
rigid  requirements — all  in  one  year;  General  Thompson 
directed  the  planning  which  resulted  in  our  enormous  war 
time  rifle  production.  At  the  basis  of  each  of  these  diffi- 
cult manufacturing  achievements  is  the  guiding  principle  of 
quality  control. 


14 


CHAPTER  XIII 
MEASUREMENT  AND   ERRORS 

The  Evolution  of  Measuring 

Measurement  is  the  foundation  upon  which  the  exact 
sciences  rest.  Since  the  manufacturing  arts  are — or  should 
be — but  the  application  of  the  laws  of  science  in  practical 
form  to  meet  our  daily  needs,  it  follows  also  that  measure- 
ment is  the  proper  starting  point  in  the  arts  just  as  it  is  in 
the  work  of  pure  science.  In  fact,  it  has  long  been  recog- 
nized that  the  degree  of  accuracy  with  which  measurements 
are  made  is  the  best  criterion  of  progress  in  the  arts.  The 
process  of  measuring  permits  comparisons  to  be  made  and 
recorded  in  form  for  use.  By  it  we  may  note  the  differences 
and  likenesses  of  similar  things,  also  the  degree  of  such  like- 
ness or  dissimilarity;  and  it  is  by  such  comparison  that  prog- 
ress can  be  recognized.  Some  changes  show  retrogression 
and  others  indicate  improvement,  but  without  the  ability 
to  measure  them  it  would  be  quite  impossible  to  advance 
either  science  or  art  in  a  way  sufficiently  systematic  for 
practical  usefulness. 

When  the  attempt  is  made  to  manufacture  a  number  of 
like  things,  some  sort  of  measuring  process  is  absolutely  in- 
dispensable. Hence  the  importance  of  understanding  what 
the  process  involves. 

The  history  of  the  development  of  the  standards  of 
measuring  (used  here  in  its  widest  sense  to  include  weighing 
or  similar  operations)  presents  a  specially  interesting  and 
fascinating  picture  of  man's  material  progress.1  It  does 

1  See  further  "  The  Progress  of  Science  as  Exemplified  in  the  Art  of  Weighing  and  Measuring," 
by  Professor  William  Harkness,  U.  S.  Naval  Observatory — presidential  address  before  the  Philo- 
sophical Society  of  Washington,  1887.  (Smithsonian  Report,  1888.) 

2IO 


MEASUREMENT  AND  ERRORS  211 

not  serve  the  present  purpose,  however,  to  digress  in  that 
direction,  other  than  to  note  the  rise  of  accuracy  that  has 
accompanied  the  evolution  of  our  present  standards.  It  is 
relatively  only  a  short  time  ago  that  the  most  precise  and 
scientific  laboratory  methods  were  quite  incapable  of  real- 
izing the  accuracy  that  is  commonly  attained  in  modern 
shop  practice,  with  much  less  effort  and  care.  Furthermore 
we  are  able  to  measure  many  things  today  that  our  forebears 
never  thought  of  measuring — and  the  end  is  not  yet. 

There  are  some  features  of  the  evolution  of  measuring, 
nevertheless,  which  must  be  considered  in  connection  with 
what  follows.  They  are  illustrative  of  the  procedure  which 
must  be  observed  in  order  to  develop  in  a  logical  way  the 
processes  of  measuring  necessary  for  controlling  quality 
in  manufacturing. 

The  Selection  of  Characteristic  Qualities  for  Measurement 

Suppose  we  assume  that  we  have  to  make  a  quantity  of 
articles — bricks  perhaps.  They  are  to  be  as  nearly  alike  as 
may  be  consistent  with  the  commercial  restriction  of  econ- 
omy. Let  it  be  assumed  also  that  we  have  no  means  or 
scheme  of  measurement.  The  first  step  necessarily  must  be 
in  the  direction  of  selecting  the  characteristics  in  which  the 
articles  are  to  agree.  These  characteristics,  which  deter- 
mine the  quality  of  the  article,  are,  of  course,  sensed  and 
evaluated  by  us  through  the  physical  means  with  which  we 
perceive  them.  Thus  if  we  were  concerned  with  bricks,  the 
essentials  would  be  shape  or  form,  size,  strength,  weight, 
surface  finish,  color,  and  so  on.  For  practical  purposes,  we 
could  get  along  very  nicely  without  paying  any  attention  to 
any  of  these  points  except  shape,  size,  and  strength,  but  as 
the  art  of  brick-making  progresses,  the  demand  increases 
for  greater  uniformity  in  the  less  utilitarian  and  more 
aesthetic  characteristics. 


212  THE  CONTROL  OF  QUALITY 

The  economist  says  that  manufacturing,  as  a  process, 
inhibits  making  beautiful  things. 

Individuality  is  the  essence  of  art;  to  be  beautiful  it  would 
seem  that  a  thing  must  bear  the  impress  of  its  maker's  personality. 
There  is  little  room  then  for  specialization  in  the  making  of  beautiful 
things.  If  we  want  the  material  apparatus  of  life  to  be  beautiful, 
we  must  be  content  with  less  of  it;  we  must  choose  between  a  great 
many  ugly  and  ordinary  things  and  a  few  beautiful  and  unique 
things.2 

This  statement  is  true  only  if  we  are  content  to  permit  it 
to  be  true.  It  should  be  a  pleasant  duty  for  the  manufac- 
turer to  dispel  this  somewhat  common,  although  fallacious 
belief,  and  the  way  to  do  it  is  by  the  first  step  just  indicated. 
Keen  and  searching  analysis  of  a  product  will  show  its  char- 
acteristic qualities,  some  of  which  contribute  to  its  useful- 
ness while  others  make  it  pleasing  to  the  senses.  Economy 
of  manufacture  reaches  its  greatest  efficiency  when  every 
characteristic  is  controlled  to  uniformity  with  deadly 
accuracy,  but  its  product  need  not  be  ugly  or  lifeless, 
unless  we  choose  to  ignore  all  but  the  most  utilitarian  quali- 
ties. If  the  model  is  beautiful,  its  beauty  can  be  repeated 
indefinitely  with  proper  care  and  attention  to  the  pertinent 
details — a  business  in  which  little  things  become  paramount. 
Is  not  the  modern  automotive  engine  an  article  of  beauty? 
It  is  made  so  by  precision  manufacturing,  which  also  makes 
it  an  article  of  commerce.  If  it  could  be  made,  and  were 
made  by  the  "individualistic"  methods  of  the  artist,  no 
ordinary  man  could  afford  to  own  one ;  nor  would  the  auto- 
motive art  have  made  such  rapid  strides. 

Standard  Samples 

Having  selected  the  characteristic  qualities  which  we 
wish  to  have  alike  in  all  the  articles  we  are  to  manufacture, 


2  Henry  Clay,  Economics  for  the  General  Reader. 


MEASUREMENT  AND  ERRORS  213 

the  next  step  involves  the  selection  of  a  standard  of  com- 
parison, and  this  standard  must  always  be  some  tangible 
physical  thing.  To  return  to  the  case  of  the  brick,  we  prob- 
ably should  select  a  brick  and  say,  "This  is  of  the  shape  and 
size  wanted.  We  will  call  this  our  standard  sample  for 
shape  and  size."  Then  perhaps  we  might  select  another  as 
the  standard  sample  to  show  the  desired  color. 

As  a  matter  of  fact,  the  method  of  comparison  by  using 
standard  samples  is  the  accepted  practice  in  more  than  one 
industry.  In  many  cases  it  has  to  be.  Take  the  matter  of 
making  cigars.  The  tobacco  must  be  graded  in  several 
ways,  as  well  as  by  odor  (and  possibly  taste),  to  secure  the 
desired  bouquet.  There  is  no  instrument  as  yet,  to  measure 
such  qualities — nor  is  there  even  a  classification  of  them. 
Any  uniformity  that  is  secured  must  be  by  comparison  with 
some  sample  or  samples  arbitrarily  selected  as  standard  as 
regards  both  raw  material  and  finished  product.  Even  if 
samples  are  not  at  hand,  they  exist  in  the  memory  of  the 
expert  whose  judgment  is  relied  upon  for  the  grading  —  and 
the  statement  still  holds  in  principle. 

Color  is  measurable,  but  the  methods  and  apparatus  find 
little  application  as  yet  outside  of  the  physics  laboratory. 
The  principal  industries  in  which  color  is  a  dominating 
quality,  such  as  the  textile  industries  and  those  of  similar 
type,  have  made  the  first  important  step  toward  standard- 
izing by  the  adoption  of  the  so-called  "  standard  color  card  " 
(see  Chapter  XXI),  which  shows  the  colors  adopted  as 
standards  in  the  form  of  classified  standard  samples. 

The  selection  of  a  standard  sample  can  hardly  be  called 
measurement.  It  is  rather  the  first  crude  step  toward 
measuring,  as  we  understand  the  term  " measuring"  when 
speaking  of  weight  or  dimension.  But  it  is  a  very  necessary 
link  in  the  chain  of  development.  Perhaps  it  may  be  asked, 
Why  carry  the  process  further  if  such  samples  will  serve  the 


214  THE  CONTROL  OF  QUALITY 

purpose?     The  answer  is  best  found  by  considering  what 
must  be  assumed  when  comparison  is  by  standard  samples. 

Dangers  of  Standard  Samples 

The  first  assumption  is  that  several  samples  are  suffi- 
ciently alike  for  practical  purposes.  If  a  number  of  samples 
are  available  to  choose  from,  this  may  reasonably  be 
assumed  to  be  true,  but  only  up  to  a  certain  degree  of  likeness. 
Further  progress  toward  general  uniformity  is  blocked 
when  that  stage  is  reached. 

The  most  dangerous  assumption  which  must  be  made, 
however,  is  that  the  standard  sample  will  not  change  with 
time.  It  is  bound  to  change.  That  is  one  of  the  few  great 
laws  of  nature  we  are  sure  of.  Everything  changes  all  the 
time,  and  very  few  samples  indeed  could  be  found  that 
would  not  alter  perceptibly — if  we  had  anything  to  use  as  a 
measure  for  detecting  the  change.  What  is  more  to  the 
point,  the  oftener  we  use  our  standard  sample  in  practice, 
the  sooner  does  it  alter  in  the  very  characteristic  for  which 
it  was  chosen  as  a  standard  of  comparison.  Our  old  friend, 
the  brick,  would  soon  wear,  and  abrade  away  from  its 
original  size  and  shape,  if  we  used  it  to  compare  with  new 
lots  of  bricks.  Also,  the  one  we  selected  as  a  sample  of  the 
desired  color  would  be  quite  sure  to  fade  with  exposure  to 
light,  or  to  grow  darker  from  handling.  At  best,  any  sys- 
tem of  uniform  manufacturing  which  is  based  on  standard 
samples  alone  requires  that  the  most  unusual  precautions 
be  taken  to  safeguard  the  standards.  The  use  of  master 
gages  and  the  care  required  in  gage-checking  may  be  in- 
stanced in  illustration. 

Measurement  by  Comparison  with  a  Standard  Scale 

The  next  move  toward  a  more  efficient  means  of  making 
comparisons  in  order  to  secure  uniformity  of  product,  is  in 


MEASUREMENT  AND  ERRORS  215 

the  direction  of  greater  general  usefulness,  simplicity,  and 
permanence  of  results.  Convenience,  if  nothing  else,  re- 
quires that  we  obtain  a  standard  of  more  general  applicability. 
Suppose  we  take  dimension  as  the  quality  to  illustrate  this. 
Once  we  assume  an  arbitrary  standard  of  length  with  a 
suitable  scale  of  divisions,  we  can  dispense  with  the  business 
of  comparing  brick  with  brick,  so  far  as  dimension  is  con- 
cerned. In  fact,  with  such  a  means  of  measurement,  we  are 
in  shape  to  compare  dimensions  by  themselves,  without 
regard  to  the  "particular  articles  whose  size  is  involved. 
Thus  the  idea  of  true  measurement  appears,  because  we  are 
able  to  reduce  our  comparisons  to  the  abstract  form  of 
figures.  Any  dimension  is  then  expressed  in  the  form : 

the  given  length 


The  measured  length 


the  standard  of  length 


The  point  to  be  borne  in  mind  is  that  when  it  becomes 
desirable  to  carry  the  control  of  quality  beyond  the  standard 
sample  stage,  the  first  step  is  to  develop  a  graded  scale  which 
will  permit  us  to  express  the  measure  of  the  quality  in  figures. 
The  latter  makes  us  reasonably  independent  of  the  dangers 
of  standard  samples.  Needless  to  say,  such  a  scale  itself  is 
always,  in  the  last  analysis,  based  on  some  tangible  and 
arbitrarily  selected  object  which  is  taken  as  the  common 
standard.  But  the  general  usefulness  and  wide  applica- 
tion of  the  selected  object  warrant  the  precautions  neces- 
sary to  insure  permanence.  Thus  dimension  and  weight, 
the  evolution  of  which  has  been  carried  to  the  practical 
limit,  may  be  taken  as  amply  safeguarded.  The  standards 
in  this  country  are  represented  by  certain  weights,  bars,  etc., 
which  are  kept  in  the  vaults  of  the  Bureau  of  Standards  in 
Washington.  (See  Figure  50.)  That  is  to  say,  all  our  meas- 
ures refer  back  to  certain  objects  which  are  arbitrarily 
selected  as  the  standards.  The  standard  of  length  is  now 


216 


THE  CONTROL  OF  QUALITY 


reproducible  for  any  reasonable  requirement  of  accuracy, 
because  its  measure  is  known  in  terms  of  light  waves. 


Figure  50.     The  Standards  of  Weight  and  Length  for  the  United 

States 
Kept  in  the  vaults  of  the  Bureau  of  Standards  at  Washington,  D.  C. 

Nevertheless  it  is  still  true  that  we  cannot  get  away  from  an 
arbitrarily  chosen  standard  even  then,  because  we  must  use 
a  given  light  wave,  such  as  sodium,  and  the  light  must  be 


MEASUREMENT  AND  ERRORS  217 

made  or  taken  from  sources  selected  as  standard,  and 
measured  with  a  certain  definitely  selected  and  calibrated 
equipment. 

The  choice  of  the  fundamental  units  for  measurement 
should  be  made  with  care.  They  should  be  convenient, 
should  permit  accurate  comparisons  with  other  quantities 
of  the  same  kind  (see  Professor  Harkness  as  referred  to 
above),  and  should  permit  of  accurate  comparisons  regard- 
less of  time  and  place.  Scientists  ordinarily  use  as  funda- 
mental units  for  physical  measurements  a  definite  length,  a 
definite  mass,  and  a  definite  unit  of  time.  Most  of  our 
ordinary  measurements  are  based  on  these  units  or  some 
combination  of  them,  e.g.,  electrical  measurements,  etc. 
Characteristic  qualities  which  are  not  measured  outside  of 
the  laboratory  as  yet,  usually  will  be  found  to  be  measurable 
in  terms  of  three  constants.  The  fact  that  sound  is  meas- 
urable in  terms  of  tone  or  pitch,  amplitude,  and  timbre  indi- 
cates a  line  of  attack  when  the  problem  arises  of  measuring 
noise  due  to  vibration.  The  color  constants  are  hue,  purity 
or  saturation,  and  luminosity  or  brightness  (see  Chapter 
XXI). 

The  Measuring  Instrument 

The  final  step  in  the  evolution  of  measurement  is  the 
development  of  instrumental  means  for  making  comparisons. 
Their  need  springs  from  the  desire  for  greater  accuracy, 
which  requires  the  use  of  something  that  is  less  subject  to 
personal  error  and  differences  from  individual  to  individual. 
This  impersonal  quality  of  the  instrument  flows  from  the 
fact  that  it  is  more  positive  in  action  than  any  unaided 
comparison  by  means  of  our  senses  can  possibly  be — a  result 
that  is  accomplished  ordinarily  by  enlarging  or  magnifying 
differences  in  reading,  so  that  errors  may  be  detected  with 
greater  ease. 


218  THE  CONTROL  OF  QUALITY 

In  using  a  finely  calibrated  scale,  for  example,  the  point 
is  soon  reached  where  finer  readings  are  impossible,  and 
further  progress  toward  greater  accuracy  is  blocked.  Sup- 
pose the  scale  is  a  high-grade  flat  steel  scale  6  inches  long, 
marked  off  in  fiftieths  and  hundredths  of  an  inch.  If  this  is 


Figure  51.     Method  of  Using  Hub  Micrometer  Caliper  #241 — -Brown  and 
Sharpe  Manufacturing  Company 

applied  in  the  attempt  to  measure  a  block  of  steel,  say, 
about  4  inches  long,  there  will  be  considerable  doubt  as  to 
which  of  two  of  the  hundredths  marks  is  the  closest  to  the 
block's  size.  If  the  block  is  longer,  the  difficulty  becomes 
greater;  and  if  it  is  longer  than  the  scale,  an  accurate  read- 
ing is  much  harder  to  obtain.  The  use  of  a  magnifying 
glass  permits  closer  reading,  but  the  use  of  an  end  measur- 
ing instrument,  which  makes  positive  contacts  in  place  of 


MEASUREMENT  AND  ERRORS  219 

side-by-side  comparison,  renders  easily  possible  a  much 
greater  precision  of  measurement. 

The  use  of  instruments  permits  the  application  of  means 
for  enhancing  errors  and  thus  permits  closer  reading.  As 
most  of  the  means  ordinarily  employed  for  accomplishing 
this  are  illustrated  in  the  following  chapters,  we  may  note 
meanwhile  only  some  of  the  features  which  such  instru- 
ments should  possess. 

No  instrument  is  worth  using  in  the  factory  unless  it  is 
sure  to  measure  more  accurately  than  can  be  done  without 
the  instrument.  At  first  thought  this  may  seem  a  common- 
place, but  it  seems  so  only  at  first  thought,  for  the  reason 
that  some  instruments  are  apparently  more  accurate  merely 
because  they  are  sensitive.  An  instrument  has  great  sen- 
sitivity when  it  answers  (or  shows  a  change  in  reading)  for 
a  very  slight  change  in  the  thing  being  measured  or  in  the 
conditions  under  which  the  measurement  is  made.  It  is 
desirable  to  note  this  difference  between  sensitivity  and 
accuracy,  because  the  two  are  sometimes  confused.  A 
balance  whose  indicating  pointer  answers  to  a  very  slight 
change  in  weight,  may  still  be  quite  inaccurate. 

The  converse  is  true  also,  because  an  accurate  instru- 
ment may  lack  sensitivity.  In  the  latter  instance  the  fact 
should  be  known,  because  it  sometimes  happens  that  the 
lack  of  sensitivity  results  in  a  lag.  It  is  therefore  important 
to  know  how  long  it  takes  a  sluggish  instrument  to  show  a 
correct  reading.  But  in  order  to  know  what  degree  of 
accuracy  an  instrument  is  capable  of  showing  it  must  be 
possible  to  check  its  precision,  and  this  requires  a  more 
exact  standard  for  checking  purposes.  It  is  for  this  reason 
that  emphasis  is  laid  on  the  necessity  for  control  centers  or 
laboratories  for  the  control  of  the  quality  concerned.  Thus 
a  later  chapter  (XVII)  deals  with  an  ideal  control  center  for 
dimension,  as  typical  of  any  su decontrol  centers. 


220  THE  CONTROL  OF  QUALITY 

In  this  discussion  of  instruments  it  will  be  noted  that  no 
attention  is  being  paid  to  certain  general  requirements  for 
measuring  apparatus  with  which  everyone  is  familiar,  such 
as  ruggedness,  precision,  facility  for  making  direct  meas- 
urements without  corrections,  general  suitability  to  the 
requirements  of  the  work,  and  so  on. 

Danger  of  Overgraduation 

It  is  desired,  however,  to  direct  attention  to  some  of  the 
qualities  in  such  instruments  which  are  frequently  over- 
looked, and  thus  make  accurate  measurements  out  of  the 
question.  One  of  these  oversights,  as  a  case  in  point,  is 
what  may  be  termed  an  "  overgraduation "  of  the  instru- 
ment. One  of  the  great  dangers  faced  by  the  technician, 
as  by  everyone  else,  is  that  of  fooling  one's  self.  It  is  vi- 
tally necessary  in  manufacturing  to  be  sure  of  the  facts — 
especially  as  to  measurement.  Therefore  an  instrument 
which  is  calibrated  to  permit  closer  readings  than  it  is  ca- 
pable of  making  is  to  be  avoided  with  care,  or  at  least  used 
with  a  knowledge  of  its  probable  errors. 

To  illustrate — the  chief  engineer  of  a  large  concern  was 
criticized  because  his  plans  said  that  certain  dimensions,  on 
tools,  should  be  held  within  .0002  inch,  the  specific  charge 
being  that  such  precision  was  uncalled  for  and  would  lead 
to  unnecessary  cost  in  the  tool-making  shops.  He  answered 
by  asking  "What  do  you  think  that  requirement  for  .0002 
inch  means?"  Of  course,  he  was  told  that  everyone  as- 
sumed it  to  mean  .0002  inch,  as  stated.  Much  to  their  sur- 
prise he  replied—  "  It  does  not.  I  intended  it  to  mean  what 
our  tool-makers  think  is  .0002  inch.  In  other  words,  what 
I  am  after  is  the  degree  of  accuracy  in  workmanship  which 
our  tool-makers  produce  when  they  think  they  are  working 
to  within  .0002  inch  of  the  stated  dimension.  If  you  think 
that  is  the  same  as  .0002  inch,  suppose  you  check  their 


MEASUREMENT  AND  ERRORS  221 

work  with  our  Pratt  and  Whitney  measuring  machine.  If 
you  do,  you  will  find  that  what  the  tool-room  thinks  is  a 
precision  of  .0002  inch  is  actually  over  twice  that,  although 
they  are  perfectly  sincere  in  their  belief.  They  are  doing 
the  best  they  can  with  the  instruments  provided,  which 
happen  to  be  calibrated  in  ten-thousandths.  These  instru- 
ments may  be  capable  of  such  accuracy,  but  as  used  in  our 
shops,  no  such  result  is  obtained." 

Every  once  in  a  while  a  factory  is  found  whose  drawings 
call  for  exceedingly  close  adherence  to  the  absolute  dimen- 
sion, although  the  shop  is  not  equipped,  except  by  the  mark- 
ings on  the  instruments,  to  work  to  any  such  degree  of  accu- 
racy as  is  prescribed.  Usually  all  hands  are  quite  sincere  in 
believing  that  they  attain  the  requirements  stated  on  the 
drawings,  but  they  merely  fool  themselves.  Why  do  so, 
however,  when  it  is  so  easy  to  possess  the  truth? 

The  Need  of  a  Final  Check 

Not  very  long  ago  the  chief  inspector  of  a  factory  whose 
work  required  a  high  order  of  accuracy  for  a  very  special 
sort  of  work  was  asked  to  produce  his  final  standard  of  di- 
mension. He  pointed  out  the  usual  standards  supplied 
with  micrometer  calipers.  His  questioner  said,  "But  I 
asked  you  to  show  me  your  final  standard — your  '  court  of 
last  appeal.' '  The  chief  inspector  blushed  and  said,  "We 
haven't  any!"  Later  he  added  in  self-justification,  "I've 
asked  for  gage  blocks  several  times,  but  they  never  gave 
them  to  me."  Does  your  chief  inspector,  by  any  chance, 
happen  to  be  in  the  same  fix? 

By  the  same  token  it  is  equally  erroneous  practice  to 
expect  accuracy  when  the  instruments  provided  do  not  per- 
mit of  close  enough  reading.  A  pressure  gage  with  a  2 -inch 
dial,  calibrated  by  5-pound  intervals,  will  hardly  permit  the 
process  to  be  held  to  closer  than  5  pounds.  Yet  just  such  a 


222  THE  CONTROL  OF  QUALITY 

case  came  to  light  during  the  recent  overhauling  of  a  process 
in  which  a  close  adherence  to  a  given  standardized  pressure 
was  vitally  important  for  securing  a  uniform  product  from 
that  process.  It  is  questionable  as  to  which  is  worse — a  me- 
chanic who  thinks  he  is  doing  accurate  work  because  an 


Figure  52.     Setting  a  Johansson  Adjustable  Limit  Snap  Gage  by  Means  of 
Johansson  Gage  Blocks 

inaccurate  instrument  says  so,  or  one  who  is  trying  to  do 
accurate  work  without  a  clear  reading  instrument  to  guide 
him.  Neither  condition  need  exist,  which  makes  their 
occurrence  all  the  more  lamentable. 

The  Choice  of  Instruments 

In  step  with  the  preceding  is  the  failure  to  realize  that 
practically  all  instruments  are  less  precise  over  a  part  of 


MEASUREMENT  AND  ERRORS  223 

their  range  than  they  are  for  the  greater  part  of  their  range. 
Furthermore,  at  the  part  of  the  range  where  greater  errors 
occur  the  measurements  are  likely  to  be  subject  to  greater 
variations  under  different  conditions  of  use.  This  is  true  in 
marked  degree  for  the  smaller  readings  of  instruments  which 
are  inherently  afflicted  with  an  initial  friction.  It  is  true 
also  for  instruments  whose  design  and  construction  involve 
backlash;  and,  naturally,  the  maximum  errors  may  occur 
where  the  backlash  may  develop  to  the  greatest  degree.  As 
an  example  of  error  resulting  from  initial  friction,  consider 
a  balance.  It  may  be  extremely  accurate  for  large  weigh- 
ings, but  will  show  very  large  errors  indeed  for  weighings 
made  at  the  threshold  of  its  scale.  Accordingly  the  smaller 
weighings  should  be  made  on  a  balance  of  smaller  total  ca- 
pacity as  the  smaller  readings  are  thus  expanded  to  a  size 
that  is  perceptible.  The  conclusion  is  inevitable,  that  the 
instrument  should  be  chosen  with  reference  to  its  capa- 
bility to  meet  the  requirements  of  a  given  situation.  It 
must  not  be  expected  to  meet  all  requirements.  You  cannot 
weigh  everything  with  one  huge  pair  of  scales.  But  the 
way  to  determine  the  suitability  of  the  instrument,  or  to 
select  a  suitable  instrument  for  a  given  purpose,  is  to  be  pre- 
pared to  check  the  work  of  that  instrument — by  some 
superior  method  of  measurement,  which  is  many  times  more 
accurate  than  the  instrument  which  is  being  checked. 
Otherwise  you  cannot  be  sure  of  your  facts. 

The  Precision  of  Measurement 

In  developing  a  method  or  process  of  measuring  it  was 
observed  that  the  first  step  involves  the  use  of  an  arbitrarily 
selected  standard  for  comparison.  Presently  a  point  is 
reached  where  observations  fail  to  agree,  and  this  point  fixes 
the  limit  of  precision  obtainable  by  such  method.  Further 
improvement  is  to  be  sought  through  devising  a  scale  of 


224  THE  CONTROL  OF  QUALITY 

more  general  applicability  which  permits  not  only  of  stating 
measurements  impersonally  in  the  form  of  abstract  figures, 
but  also  securing  an  additional  degree  of  accuracy  in  most 
cases.  This  method  also  soon  reaches  its  limit  of  precision, 
and  further  progress  toward  more  exact  measurement  must 
make  use  of  still  more  impersonal  methods  by  means  of  in- 
struments. While  this  last  step  usually  gains  much  greater 
fidelity  to  the  absolute  measurement,  nevertheless  it  too 
reaches  an  ultimate  limit  of  precision  beyond  which  meas- 
urements of  the  same  thing  under  like  conditions  are  not  in 
agreement.  This  situation  follows  an  earlier  stage  where 
measurements  by  different  observers,  working  under  the 
same  or  slightly  different  circumstances,  do  not  check. 

Thus  Langley,  in  the  discussion  of  small  irregularities  of 
his  bolometer  records  of  the  solar  spectrum,  said  :3 

When  we  approach  the  limits  of  vision  or  audition,  or  of  per- 
ception by  any  other  of  the  human  senses,  no  matter  how  these  may 
be  fortified  by  instrumental  aid,  we  finally  perceive,  and  always 
must  perceive  a  condition,  a  condition  still  beyond,  where  certitude 
becomes  incertitude,  although  we  may  not  be  able  to  designate 
precisely  where  one  ceases  and  the  other  begins.  This  is  always 
the  case,  it  would  seem,  on  the  boundaries  of  our  knowledge  in  every 
department,  and  it  is  so  here. 

Inevitably,  then,  a  certain  critical  point  is  reached  for 
any  given  set  of  conditions,  where  errors  enter,  and  this  is 
entirely  apart  from  the  ever-present  assurance  of  occasional 
accidental  errors.  Of  course  we  know  that  errors  are  bound 
to  occur — the  theme  of  our  study  has  been  throughout  that 
quality  is  varying  continually — consequently  the  readings 
of  our  measurements  of  quality  will  vary. 

The  term  "precision"  is  a  confession  that  absolutely 
correct  measurement  is  impossible  of  realization.  Accuracy 
means  exact  conformity  to  the  absolutely  true  standard. 

3  Joel  Stebbins,  "Observation  vs.  Experimentation,"  Science,  January  13,  1922. 


MEASUREMENT  AND  ERRORS  225 

Absolute  accuracy  implies  freedom  from  error,  hence  for 
practical  purposes  we  are  forced  to  speak  of  the  degree  of 
accuracy  rather  than  of  accuracy  itself.  "Precision"  is  a 
shorter  term  than  "degree"  or  "rate  of  accuracy,"  and 
means  the  same  thing.  Consequently  precision  is  a  per- 
centage of  the  measurement.  Thus,  the  precision  of  Swed- 
ish gage  blocks  is  stated  as,  say,  one  hundred  thousandth  of 
an  inch  per  inch  of  length;  and,  strictly  speaking,  we  should 
always  state  precision  in  that  form.  The  attitude  of  the 
physicist  toward  these  terms  is : 

When  the  true  value  is  known  the ' '  Accuracy ' '  may  be  expressed 
as  the  difference  between  the  experimental  quantity  obtained  and 
this  true  value.  Since,  however,  the  exact  or  true  value  is  seldom 
known,  the  accuracy  of  the  result  cannot  be  stated,  and  it  becomes 
the  more  imperative  to  have  methods  of  estimating  the  precision 
measure  or  reliability  of  the  result  of  a  series  of  observations.4 

Precision  of  Workmanship 

Now,  just  as  there  is  a  limit  to  the  precision  of  measure- 
ment for  any  given  situation,  so  is  there  a  limit  to  the  pre- 
cision of  workmanship  that  is  possible  for  any  given  process 
or  operation.  And  this  limiting  precision  in  manufacture 
follows  after  and  is  dependent  upon  the  attainable  precision 
of  measurement  of  the  work  produced  by  said  process, 
whether  the  measurement  be  made  by  a  highly  developed 
instrument  or  by  mere  visual  comparison  with  a  standard. 
What  is  true  of  the  possible  precision  is  equally  true  of  the 
precision  that  it  is  sensible  to  use  commercially,  for  cost  will 
enter  as  the  determining  factor  in  the  selection  of  the  degree 
of  accuracy  best  suited  to  a  particular  case.  It  is  usually 
true,  however,  that  a  decidedly  higher  precision  can  be 
obtained  with  little  effort,  if  the  effort  is  properly  made. 

Whether  the  attempt  to  increase  precision  should  be 

4  "  Precision  of  Measurements,"  by  Professors  George  V.  Wendell  and  W.  L.  Severinghaus  of 
Columbia  University. 

15 


226  THE  CONTROL  OF  QUALITY 

made  is  a  matter  of  business  judgment,  and  calls  for  a  sen- 
sible decision.  A  military  gun  stock  demands  much  closer 
fidelity  to  accurate  dimension  than  does  wooden  furniture, 
but  it  would  save  a  deal  of  profanity  if  desk  drawers  did 
not  stick.  The  stores  are  full  of  all  kinds  of  goods  that  indi- 
cate the  same  situation.  It  is  a  mistake  to  say  that  any- 
thing is  good  enough,  for  there  must  be  some  one  dimension, 
for  example,  that  is  best  suited  to  any  special  case.  If  the 
article,  as  designed,  is  best  suited  to  the  job,  the  manufac- 
turer's constant  endeavor  should  be  to  obtain  a  closer  and 
closer  adherence  to  this  ideal  standard.  This  means  the 
refinement  of  manufacturing  through  the  reduction  of  errors 
—an  undertaking  that  should  be  inaugurated  by  a  study  of 
errors  themselves. 

The  Theory  of  Errors 

The  most  valuable  thing  to  realize  about  errors,  so  it 
would  seem,  is  that  they  always  have  a  tendency  to  occur. 
They  follow  the  general  rule  that  it  is  easier  to  be  bad  than 
it  is  to  be  good.  Their  number  can  be  reduced  only  by  the 
vigilant  use  of  foresight,  care,  and  thoroughness.  More- 
over, like  a  snowball  rolling  downhill,  they  tend  to 
accumulate  others  of  their  own  kind;  so  that  an  ounce  of 
prevention  is  worth  many  pounds  of  cure. 

A  knowledge  of  the  theory  of  errors  is  so  important  in 
accurate  physical  measurements  that  considerable  atten- 
tion has  been  given  to  it,  and  several  substantial  literary 
contributions  have  been  made.  The  application  of  their 
conclusions  are  too  much  confined  to  the  physics  laboratory, 
however,  and  should  be  more  generally  understood  by  man- 
ufacturers. The  physicist  starts  off  by  making  a  distinction 
at  once  between  mistakes — that  is,  mere  blunders — and 
errors.  In  the  factory,  mistakes  are  the  order  of  the  day, 
and  their  best  prevention  lies  in  the  direction  of  checks  by 


MEASUREMENT  AND  ERRORS  227 

independent  methods  of  one  sort  or  another,  as  has  been 
indicated  early  in  this  work. 

Individual  vigilance  and  the  habit  of  doing  everything  in  a 
careful  and  orderly  manner  are  the  only  means  of  reducing  such 
inaccuracies  to  a  minimum.  It  is  often  highly  advisable  to  run 
some  rough  independent  check  experiment  or  to  test  the  final  re- 
sults with  common  sense  to  see  that  no  gross  blunder  has  been 
committed.5 

Professor  H.  M.  Goodwin,  in  his  "Precision  of  Meas- 
urements and  Graphical  Methods,"  classifies  errors  as  deter- 
minate errors,  whose  value  can  be  determined  and  their 
effects  eliminated,  and  indeterminate  errors.  He  classifies 
determinate  errors  as: 

1.  Instrumental  errors,  due  to  faulty  adjustment  or 

construction  of  the  measuring  instrument. 

2.  Personal  errors,  due  to  the  " personal  equation"  of 

the  observer. 

3.  Errors  of  method  or  theoretical  errors,  due  ordinarily 

to  using  an  instrument  under  conditions  for  which 

its  graduations  are  not  standard  or  correct. 

» 

It  will  be  observed  that  some  errors  lead  to  incorrect  con- 
clusions, in  spite  of  the  fact  that  several  measurements  may 
be  in  agreement.  Thus  if  the  instrument  is  out  of  adjust- 
ment, or  if  the  observer  is,  by  nature,  generous  in  his  read- 
ings, so  that  he  constantly  errs  on  the  high  side  of  the 
measurement,  or  if  the  instrument  is  standard  at  68°  F. 
but  is  used  at  90°  F.,  the  measurements  may  in  all  cases 
agree  and  still  all  be  in  error. 

As  to   indeterminate  errors — accidental   or  residual- 
Goodwin  says: 

Experience  shows  that,  when  a  measurement  is  repeated  a 
number  of  times  with  the  same  instrument  and  by  the  same  observer 

5  "  Precision  of  Measurements,"  by  Professors  George  V.  Wendell  and  W.  L.  SeverinRhaus 
of  Columbia  University. 


228 


THE  CONTROL  OF  QUALITY 


under  apparently  the  same  conditions,  the  results  usually  differ  in 
the  last  place  or  sometimes  last  two  places  of  figures.  Thus  in  sO 
simple  a  measurement  as  the  determination  of  the  distance  between 
two  lines  with  a  scale  graduated  in  millimeters,  successive  measure- 
ments will  not  agree  to  one-tenth  millimeter  if  fractions  of  a  milli- 
meter are  estimated  by  the  eye. 

Such  errors  have  been  found  to  follow  the  law  of  chance, 
which  may  be  plotted  graphically,  as  shown  in  Figure  53, 
from  the  equation: 


in  which  y  is  the  frequency  of  occurrence  of  an  error  of 
magnitude  x,  h  is  a  constant  related  to  the  reliability  of  the 
observations  and  called  the  "precision  index,"  e  is  the  Na- 
perian  logarithmic  base  (2.7183),  and  ir  is  the  constant, 
3.1416. 

It  will  be  observed  from  the  curve  that: 

First — Small  errors  occur  more  frequently  than  large  ones ; 
Second — Very  large  errors  are  unlikely  to  occur; 
Third — Positive  and  negative  errors  of  the  same  numerical 
magnitude  are  equally  likely  to  occur. 


V7T 


Figure  53.     Probability  Curve,  Showing  the  Frequency  of 
Occurrence  of  an  Error 


MEASUREMENT  AND  ERRORS  229 

When  Theory  and  Practice  Differ 

This  law  assumes  an  infinite  number  of  observations, 
but  is  reasonably  true  in  most  cases  for  a  comparatively 
small  number — hence  its  value  as  a  guide.  It  presupposes, 
however,  that  the  observer  is  trying  to  attain  absolute  accu- 
racy as  nearly  as  may  be;  and,  in  the  case  of  factory  work- 
manship, this  is  where  practice  frequently  departs  from 
theory.  Being  sane,  the  workman  will  do  what  he  believes 
to  be  to  his  own  best  interest.  Consequently  if  there  is  a 
penalty  attached  to  spoilage  of  work,  he  will  deliberately 
keep  on  the  safe  side,  since  in  that  way  he  has  a  chance  to 
repair  his  errors. 

Consider  for  a  moment  the  case  of  a  2-inch  shaft  which 

has  a  tolerance  of  .0004  inch.     If  the  limits  are  set 

o 

inch  (i.e.,  allowed  .0004  inch  over  and  o  under  dimen- 
sion) the  greater  part  of  the  work  will  hug  2.0004  inch, 
because  the  operator  will  stay  on  the  safe  side  and  work 
toward  the  full  dimension.  If  that  is  what  is  desired,  well 
and  good;  otherwise  the  tolerance  should  be  split  up  to 
allow  for  this  tendency.  In  closer  work  especially,  it  would 

be  better  practice  to  set  the  limits  as  -        -  inch  instead 

.0002 

OOO2 

of  :         :  inch,    or    ±    .0001    inch.     The    probability    and 

chance  would  thus  favor  securing  more  work  to  the  desired 
ideal  of  2.0000  inch. 

If  all  errors  were  equally  distributed  as  to  size  and  occur- 
rence, plus  or  minus,  they  would  cancel  each  other  to  a  large 
extent.  In  the  factory  they  do  not  do  so,  but  accumulate 
too  rapidly  for  comfort.  There  are  several  ways  in  which 
this  occurs,  and  happily  there  are  several  ways  to  meet  the 
situation. 


230  THE  CONTROL  OF  QUALITY 

The  Chain  of  Inaccuracy 

First,  there  is  what  may  be  termed  a  "chain  of  inaccu- 
racy" due  to  slip  in  the  transfer  of  measurements.  The 
master  or  reference  gage  is  not  quite  like  the  model,  the 
reference  gage  template  is  not  quite  like  the  gage,  and  so  on. 
This  error  is  negligible  when  a  very  precise  method  of 
measurement  is  available  for  checking  purposes. 

The  Chain  of  Wear 

Then  there  is  a  chain  of  wear,  resulting  in  systematic  and 
progressively  increasing  error.  Granting  the  availability  of 
more  precise  control  apparatus,  the  remedy  for  such  errors 
also  is  checking  with  sufficient  frequency.  As  to  the  me- 
chanical side  of  intentionally  lessening  wear,  there  is  room 
for  considerable  discussion  and  the  resulting  conclusions  are 
widely  applicable — to  tools,  to  measuring  devices,  and  to 
the  product  itself.  Professor  John  E.  Sweet  was  the  great 
apostle  in  this  field  as  in  many  other  practical  problems. 
In  1876  or  before,  he  advocated  the  use,  and  pointed  out  the 
advantages  of  equal  length  wearing  surfaces;  viz.,  the  first 
"straight-line"  engine  had  a  cross-head  and  guides  of  equal 
length,  which,  after  years  of  use,  showed  practically  no  wear. 
In  1903,  he  stated,  "  Things  that  do  not  tend  to  wear  out  of 
true  do  not  wear  much."  This  principle  is  worthy  of  much 
consideration.  In  connection  with  it  the  present  tendency 
toward  the  use  of  gages  with  wider  and  larger  anvils — or 
gaging  points — may  be  noted  although  it  is  true  the  use  of 
such  gages  is  to  be  attributed  in  part  to  other  causes  than 
minimum  wear,  inasmuch  as  they  tend  to  give  more  accu- 
rate results,  by  lessening  the  chance  of  applying  the  gage  at 
an  angle. 

Incidentally,  it  may  be  noted  that  we  may  profitably 
extend  the  above  principle  to  include  the  idea  of  even  wear 
for  a  number  of  like  parts.  Thus  if  everything  wore  at  the 


MEASUREMENT  AND  ERRORS  231 

same  rate,  progressive  errors  would  accrue,  but  their  effect 
would  be  less,  due  to  the  averaging  process  going  on,  and 
thus  tending  to  hold  to  uniformity.  Take  a  multicylinder 
automotive  engine — if  one  of  the  several  piston  gudgeon 
pins  is  a  poor  fit,  all  will  tend  to  wear  out  of  adjustment. 
Suppose,  even,  that  all  the  pins  are  fitted  with  beautiful 
exactness  by  hand-reaming,  but  that  some  are  larger  than 
others.  Will  they  wear  evenly?  Will  they  continue  to  re- 
main in  adjustment  as  perfectly  as  if  all  were  almost  exactly 
alike?  Furthermore,  not  only  does  the  idea  of  even  wear 
bear  upon  this  matter  of  uniform  dimension,  but  also  upon 
the  question  of  uniform  hardness,  uniformity  of  material, 
quality  of  finish,  and  so  on. 

The  Cure  for  Errors 

The  cures  for  most  errors  will  suggest  themselves  as  soon 
as  a  systematic  effort  is  made  to  locate  and  determine  their 
causes.  Whenever  possible  they  must  be  hunted  down  and 
stamped  out  at  the  source.  Some  errors  may  be  reduced 
by  putting  processes  under  uniform  control,  and  in  particu- 
lar by  averaging  the  errors  through  spreading  them  out 
evenly.  The  experience  of  Whitworth  in  creating  the  first 
accurate  surface  plate  reveals  a  valuable  lesson.  Taking 
three  plates,  alternately  comparing  them  by  contact,  and 
then  scraping  off  the  high  spots,  he  used  the  errors  to  de- 
stroy each  other  and  thus  created  the  basis  of  all  our  machine 
shop  precision — a  true  plane  surface,  relatively  speaking. 

The  concluding  observation  to  be  drawn  from  the  study 
of  measurement  and  of  errors,  beside  the  very  obvious  neces- 
sity for  care  and  thoroughness  as  to  every  detail,  is  the  need 
of  providing  control  apparatus  for  the  qualities  with  which 
we  are  concerned.  To  be  effective,  such  apparatus  must 
be  safeguarded,  and  even  then  it  is  useful  only  in  so  far  as  its 
use  and  the  conditions  surrounding  its  application  are  freed 


232  THE  CONTROL  OF  QUALITY 

from  possible  causes  of  error.  The  ideal  dimensional  con- 
trol center  or  dimensional  laboratory  to  be  described  in 
Chapter  XVII,  is  to  be  considered  as  a  guide  to  what,  in 
principle,  any  such  control  laboratory  should  be,  regardless 
of  the  quality  concerned.  Dimension  has  been  chosen  as 
the  type  merely  because  dimensional  control  has  been  car- 
ried to  a  higher  degree  of  precision  and  its  apparatus  is  more 
highly  developed  than  is  the  case  with  most  other  qualities 
— such  as  color,  for  example.  This  condition,  it  seems  prob- 
able, will  be  modified  as  time  goes  on,  and  more  and  more 
qualities  are  brought  to  the  same  state  of  accurate  control.6 
The  fact  that  means  do  not  exist  at  the  moment  for 
measuring  some  of  the  characteristic  qualities  with  which 
industry  is  concerned,  merely  serves  to  indicate  the  direc- 
tion in  which  the  start  should  be  made  toward  conscious 
improvement  of  these  qualities.  If  industry  makes  the 
demand  on  science  to  develop  principles,  practices,  and 
equipment  to  meet  its  requirements,  the  needful  things  that 
are  lacking  at  present  will  be  supplied. 

6  The  principle  of  measurement,  in  fact,  is  being  extended  to  evaluate  the  functions  of 
management.     See  an  editorial  by  L.  P.  Alford  in  Management  Engineering,  Nov.  1921. 


CHAPTER  XIV 
QUALITY  DEFINED— THE  IDEAL  STANDARD 

Characteristic  Qualities  of  Product  Must  Be  Known 

Thus  far  we  have  considered  the  subject  of  quality  in  its 
various  relationships  and  have  traced  the  basic  influence  of 
measurement  in  order  to  prepare  the  way  for  a  better  under- 
standing of  quality  itself.     We  are  now  in  a  position  to  ask 
— "What  is  it  that  constitutes  quality?" 

The  first  answer  is  that  each  attribute  or  characteristic — • 
shape,  dimension,  strength,  finish,  color,  and  so  forth — 
which  defines  one  kind  of  article  is  a  quality  of  that  article. 
The  more  definite  and  specific  we  make  the  descriptions  of 
the  dominating  qualities,  the  more  accurately  do  we  under- 
stand just  what  the  product  is  intended  to  be,  and,  inciden- 
tally, wherein  it  is  to  differ  from  other  articles  of  the  same 
general  class  of  goods.  To  state  a  quality  at  all  accurately, 
it  must  be  compared  with  some  arbitrarily  selected  standard. 
For  example,  we  might  say  a  rod  is  to  have  length,  but  we 
have  not  described  the  rod  as  regards  dimension  until  we 
state  the  relationship  between  its  length  and  that  of  some- 
thing else.  We  can  secure  a  more  exact  definition  of  the 
dimensional  quality  of  the  rod  if  we  say  that  its  length  is  to 
be  the  same  as  that  of  a  sample  rod  which  has  been  selected 
as  standard.  But,  as  a  matter  of  fact,  in  this  case  the 
comparison  would  be  made  with  the  well-accepted  standard 
of  dimension  and  the  length  stated  in  standard  units  of  feet, 
inches,  or  both,  depending  on  convenience. 

This  well-known  and  seemingly  elementary  example  is 
simple  only  because  we  have  a  thoroughly  established  and 
well-known  method  of  comparison  or  measurement  for 

233 


234  THE  CONTROL  OF  QUALITY 

dimensional  quality;  but  what  about  some  of  the  other 
qualities?  With  respect  to  color,  for  instance,  there  is,  as 
yet,  no  accepted  method  of  analysis  and  comparison  with  a 
standard.  To  say  an  article  is  to  be  painted  red  is  nearly  as 
loose  a  definition  of  color  quality  as  to  describe  dimensional 
quality  by  saying  that  a  rod  had  length — because  there  can 
be  an  enormous  number  of  tints  and  shades  of  red.  In  the 
absence  of  a  color  scale  for  numerical  comparison,  we  are 
reduced  to  saying  that  the  color  will  be  like  a  given  standard 
sample.  We  must  also  take  precautions  to  see  that  the 
color  of  the  sample  itself  does  not  change  in  the  course  of 
time,  and  thereby  carry  the  product  away  from  the  standard 
as  originally  set. 

The  question  of  whether  such  qualities  as  color  can  be 
reduced  to  a  basis  of  definite  measurement  with  the  same 
ease  of  treatment  as  dimension  must  be  deferred,  at  this 
time.  Meanwhile,  dimension  will  be  used  chiefly  to  illus- 
trate the  discussion  as  it  proceeds.  It  should  be  borne 
in  mind,  however,  that  the  general  principle  applies  to  the 
treatment  of  all  qualities,  that  no  quality  can  be  described 
without  comparing  it  to  some  standard — which  process  is 
measurement — and  that  the  application  of  the  idea  of  meas- 
urement must  not  be  confined  to  dimension  alone.  This  is 
one  excellent  reason  why  every  industrial  executive  who 
is  interested  in  the  subject  under  discussion  should  be 
familiar,  in  a  general  way  at  least,  with  the  principles  under- 
lying the  precision  of  measurement  and  the  theory  of  errors 
—to  secure  an  important  attitude  of  mind  and  a  necessary 
sense  of  discrimination,  of  proportion  and  perspective. 

Quality  Varies  Continually 

One  of  the  first  things  that  this  knowledge  will  reveal  is 
that  there  is  no  such  thing  as  an  absolutely  accurate  measur- 
ment.  No  matter  how  carefully  the  unknown  is  com- 


QUALITY  DEFINED— THE  IDEAL  STANDARD 


235 


pared  with  an  accepted  standard,  errors  are  bound  to  creep 
in;  and  very  shortly  a  certain  critical  point  is  reached  be- 
yond which  these  errors  can  be  reduced  only  through  the  use 
of  extreme  precautions,  if  at  all. 

This  thought  leads  at  once  to  one  of  the  most  important 


Figure   54. 


Checking  Johansson   Adjustable  Limit   Plug  Gage  with   Gage 
Blocks  Mounted  in  Holder 


conceptions  of  what  constitutes  quality,  an  idea  that  must 
be  kept  in  mind  throughout  the  subsequent  study  of  the 
control  of  quality,  namely,  that  quality  is  a  variable. 
Quantity  relates  to  the  product  en  masse,  and  in  this  sense 
is  abstract  and  impersonal.  Quality,  however,  is  different 
for  each  separate  article  produced.  Hence  the  quality  of 
the  factory  product  varies  from  piece  to  piece.  This  fact 
must  be  clearly  appreciated  before  an  attempt  is  made  to  fix 


236  THE  CONTROL  OF  QUALITY 

upon  the  standards  of  quality  desired,  or  to  take  up  the  con- 
sideration of  the  organization  and  arrangement  of  manu- 
facturing equipment  and  methods  most  suitable  for  securing 
these  desired  standards  with  greatest  economy.  In  prac- 
tice, the  degree  of  quality  varies  continually  from  the 
standard  desired.  Further,  the  degree  of  quality  varies 
with  respect  to  time,  in  the  sense  that  the  attempt  to  make 
many  things  alike  results  inevitably  in  quality  gradually 
slipping  away  from  this  desired  standard  as  the  work  pro- 
ceeds. This  tendency  of  quality  in  all  its  forms  to  vary  and 
change  is  always  present  as  a  potential  force,  and  acts  ex- 
cept in  so  far  as  it  is  held  in  check  by  external  means  pro- 
vided for  control  purposes. 

Development  of  the  Design 

With  the  preceding  in  mind,  it  should  be  apparent  that 
the  study  of  the  control  of  quality  must  begin  with  an  in- 
tensive study  of  the  product,  from  which  should  result  what 
is  ordinarily  called  the  "design."  Now  the  production  of 
almost  anything,  let  alone  making  accurately  uniform  arti- 
cles, presupposes  a  definite  standard,  usually  represented  by 
drawings,  specifications,  or  a  model;  but  preferably  by  all 
three.  This  standard  is  purely  ideal  and  cannot  be  repli- 
cated exactly  in  quantity,  because  the  absolute  is  unat- 
tainable. Nothing  ever  was  made  in  exact  accordance  with 
the  ideal  design,  or  ever  will  be. 

Under  given  conditions,  the  time  and  cost  of  production 
in  quantity  varies  with  the  degree  of  accuracy  to  the  ideal 
standard  that  is  required.  Hence  the  art  of  the  designing 
engineer  and  of  the  production  engineer  is  called  into  play  to 
fix  upon  manufacturing  standards,  which  vary  from  the  ideal 
by  certain  differences  or  allowed  errors.  This  process  sets 
limits  which  constitute  a  tolerance  for  the  actual  fabrication 
of  the  work.  Returning  to  the  example  of  the  rod,  the  com- 


QUALITY  DEFINED— THE  IDEAL  STANDARD  237 

plete  design  would  state  its  length  as  so  many  inches  plus  or 
minus  certain  stated  limits,  or  allowable  errors. 

By  way  of  summary,  suppose  now  that  we  reverse  the 
preceding  order  for  the  purpose  of  more  clearly  developing 
the  following  definitions: 

1.  The  complete  design  (which  will  be  referred  to  simply 
as  the  "  design  ")  is  the  exact  description  of  the  product,  and 
therefore  sets  forth  in  detail  (with  allowed  variations  from 
exact   measurements)    the  characteristics  of  all   essential 
qualities,    i.e.,    the   manufacturing   standards.     This   pre- 
supposes, of  course,  that  the  product  has  been  thoroughly 
analyzed  and  that  a  list  of  the  desired  quality  characteristics 
has  been  made. 

2.  The  " ideal  standard"  is  the  bare  design  without  the 
allowed  variations,  and  consequently  is  merely  the  outline 
or  shell  of  what  the  ideal  product  would  be  if  quality  were 
not  a  variable. 

3.  The  " theoretical  standard"  is  what  the  ideal  stand- 
ard would  be  if  it  were  designed  with  a  view  solely  to  obtain- 
ing the  best  article  for  the  purpose  for  which  the  product 
is  intended  without  regard  to  cost;  i.e.,  it  is  the  100  per  cent 
standard  for  the  class  of  articles  to  which  the  product  be- 
longs. 

It  is  hardly  proper  to  call  these  concepts  by  the  formal 
name  of  " definitions,"  as  they  have  no  special  significance 
except  as  a  means  of  avoiding  misunderstanding  of  the 
following  consideration  of  some  ideas  about  design  that  are 
essential  to  our  purpose. 

The  Theoretical  Standard 

The  principal  value  of  the  theoretical  or  100  per  cent 
standard,  to  which  attention  was  directed  in  Chapter  II,  is 
to  provide  something  to  which  we  can  refer  in  improving  the 
product,  as  time  goes  on  and  such  improvements  are  com- 


238  THE  CONTROL  OF  QUALITY 

mercially  practicable.  The  latter  are  always  desirable,  if 
the  selling  price  is  not  increased  thereby.  The  manufac- 
turer who  has  a  well-rounded  out  idea  of  what  his  product 
would  be  if  it  were  the  100  per  cent  article  of  its  class,  is 
better  able  to  guide  future  progress,  also  to  know  in  what 
directions  such  progress  should  take  place.  Incidentally 
he  may  avoid  the  predicament  of  the  modest  advertiser  who 
illustrates  a  "perfect"  product,  only  to  announce  incon- 
sistently with  each  new  season,  an  improvement  of  an  al- 
ready perfect  thing — and  this  to  a  purchasing  public  which 
is  becoming  increasingly  critical  and  whose  discrimination 
is  ever  more  intelligently  applied. 

No  mention  has  yet  been  made  of  one  of  the  greatest  ad- 
vantages in  having  a  theoretically  perfect  standard  to  guide 
the  development  of  a  design — namely  it  will  help  to  coun- 
teract the  danger  of  copying  the  errors  of  the  past,  by 
blindly  doing  things  as  they  have  been  done  before. 

Professor  John  E.  Sweet 1  expressed  the  idea  as  follows : 

Whoever  designs  a  new  machine  or  an  improvement  on  an  old 
one  conceives  of  some  feature  or  ruling  object  of  his  design  or  some 
feature  that  is  an  improvement  on  present  practice  and  neglects  the 
other  features — simply  follows  common  practice  without  consider- 
ing whether  the  other  features  may  not  be  as  open  to  improvement 
as  the  special  feature  he  is  working  out.  .  .  .  And  it  all  comes 
from  following  habit,  without  reason  ...  it  is  only  those  who 
come  to  think  of  the  best  way  who  are  likely  to  do  the  best;  and 
those  also  who  think  that  the  "best  way  is  bad  enough." 

It  happens  too  often  that  betterment  of  the  product  is 
blocked  by  prohibitive  cost,  simply  because  the  designer 
either  was  not  informed  as  to  the  probable  direction  such 
improvement  would  follow,  or  failed  to  take  it  into  consider- 
ation in  designing  earlier  models.  With  a  wider  and 
farther-seeing  perspective,  he  would  have  been  able  to  shape 

'John  E.  Sweet,  "Things  That  Are  Usually.Wrong." 


QUALITY  DEFINED— THE  IDEAL  STANDARD 


239 


his  design  and  make  his  factory  arrangements  so  as  both  to 
meet  the  present  needs  and  to  be  adapted  readily  for  an  im- 
proved product  when  the  time  is  ripe  for  such  refinement. 

The  Ideal  Standard 

The  outline  or  skeleton  design,  without  statement  of  the 
permissible  variations,  is  here  called  the  "ideal  standard" 
—it  is  ideal  in  the  sense  that  it  cannot  be  realized  exactly  in 
practice  in  spite  of  the  fact  that  it  is  the  desired  standard. 
As  a  matter  of  fact,  one  article  might  be  made  so  very 
nearly  like  the  ideal  that  the  errors  could  not  be  detected  by 
the  available  means  of  measurement,  but  its  cost- 'would 


Figure  55.     Use  of  Johansson  Gage  Blocks  and  Sine  Bar  to  Check  Taper  of  a 
Milling  Cutter  Shank 


240  THE  CONTROL  OF  QUALITY 

place  it  beyond  the  pale  of  commercial  possibilities.  A 
great  telescope  is  an  example  of  the  sort.  But  the  construc- 
tion of  two  such  articles  alike  to  the  same  degree  of  exact- 
ness would  markedly  increase  the  effort  required,  even  if  it 
were  possible.  The  manufacture  of  many  such  articles 
would  increase  the  problem  enormously,  and  any  attempt 
to  avoid  errors  wholly  would  certainly  fail.  On  the  other 
hand,  a  relatively  slight  releasing  of  the  requirements  for 
accuracy  renders  the  task  much  simpler,  so  that  it  becomes 
a  true  manufacturing  proposition.  In  fact  it  is  possible  to 
set  a  very  high  standard,  provided  the  conditions  of  the 
problem  are  appreciated  and  proper  precautions  taken  at 
the  start  to  meet  them. 

To  admit  that  the  ideal  or  desired  standard  cannot  pos- 
sibly be  realized,  may  at  first  appear  like  an  attitude  of 
hopelessness,  but  that  is  not  the  fact.  All  progress  requires 
that  we  have  in  mind  some  rather  definite  ideals,  which  we 
are  trying  to  realize.  It  detracts  in  no  degree  from  the  im- 
portance of  the  effort  to  realize  these  ideals,  if  it  is  admitted 
that  at  best  it  will  result  only  in  approximation  to  them. 
The  fact  remains  that  before  we  attempt  to  make  anything, 
we  should  know  what  we  are  trying  to  make ;  and  however 
thoroughly  we  may  know  this  ourselves,  it  is  equally  im- 
portant that  we  describe  it  so  clearly  that  all  concerned  in 
the  work  may  know  what  we  wish  done.  The  more  def- 
inite, exact,  and  complete  this  preliminary  description 
which  makes  up  the  skeleton  design,  the  greater  will  be  the 
economy  of  effort,  materials,  and  time  in  the  work  of  con- 
struction. 

Progress  Toward  More  Exact  Designs 

The  increasing  tendency  toward  the  more  specific 
and  complete  definition  of  qualities  is  easily  traced.  It  is 
not  necessary  to  hark  back  very  far  in  the  development  of 


QUALITY  DEFINED— THE  IDEAL  STANDARD 


241 


engineering  to  reach  a  point  where  the  design  was  developed 
in  large  part  as  the  work  progressed.  There  is  a  quite 
credible  story  to  the  effect  that  early  wooden  shipbuilding 
was  carried  on  in  two  stages  of  hull  construction.  The 


Figure  56.     Set-Up  of  Johansson  Blocks  for  Checking  Taper  of  a  Special  Plug 

Gage 

shipbuilder  first  erected  the  parallel  middle  body,  after 
which  the  construction  of  the  bow  and  stern  was  taken  up 
by  a  ' ' bow-and-stern  gang."  Such  a  gang  traveled  from 
yard  to  yard,  sized  up  the  job  as  it  stood,  perhaps  made  a 
rough  sketch  on  a  piece  of  plank,  and  with  this  general 
understanding  proceeded  to  erect  a  bow  and  a  stern  to 
suit  the  work  already  in  place.  This  method  certainly 


16 


242  THE  CONTROL  OF  QUALITY 

had  the  advantage  of  simplicity,  to  say  nothing  of  reducing 
overhead  expense. 

An  examination  of  the  early  designs  and  construction 
plans  in  any  of  our  oldest  machine  shops,  shows  nearly  the 
same  degree  of  rough-and-ready  methods.  There  is  much 
sad  experience  to  be  read  between  the  lines  in  following  up 
the  evolution  of  the  present-day  drawing  from  its  crude 
start,  through  the  later  addition  of  more  and  greater  refine- 
ments, until  we  arrive  at  the  finished  plans  of  the  modern 
highly  organized  drafting-room.  Notice  that  the  tendency 
is  toward  an  ever-increasing  exactness  and  completeness  in 
showing  the  details  of  what  is  wanted.  We  have  learned,  in 
short,  that  it  is  cheaper  to  make  our  mistakes  on  paper  than 
to  have  to  correct  them  in  the  materials  of  construction  as 
the  work  progresses. 

The  same  development  is  to  be  noted  in  the  specifica- 
tions or  written  descriptions  that  supplement  the  drawings, 
although  not  to  the  same  extent,  for  even  today  most 
specifications  contain  ambiguous  language.  The  wise 
manufacturer,  while  preparing  his  estimates,  will  be  careful 
to  iron  out  as  far  as  possible,  before  starting  work,  such  ex- 
pensive little  pitfalls  as  "small  surface  scratches  on  this 
part  will  be  permitted  in  the  judgment  of  the  inspector,"  or 
"  variations  in  other  dimensions  will  be  allowed,  but  the 
work  must  be  to  the  purchaser's  satisfaction." 

Changes  in  Design  Must  Be  Avoided 

This  lesson  of  past  experience  in  design  and  manufac- 
ture has  been  paid  for  dearly.  It  teaches  quite  clearly  that 
the  time  to  make  up  our  minds,  as  well  as  to  do  a  lot  of 
thinking,  is  before  commencing  to  make  chips.  But  even 
with  the  full  knowledge  of  this  principle  before  us,  is  it 
rigorously  applied?  In  the  majority  of  enterprises  it  is  not 
so  applied,  and  the  particular  way  in  which  it  is  violated 


QUALITY  DEFINED— THE  IDEAL  STANDARD  243 

most  seriously  may  be  summed  up  by  the  word  ' '  changes ' ' 
—the  great  killer  of  economy  in  manufacturing,  whether  it 
be  of  ships,  automobiles,  firearms,  or  what-not. 

The  design  should  be  made  with  an  open  mind  and  the 
designer  given  the  widest  latitude  while  he  is  designing. 
Further,  a  method  of  attack  has  been  indicated  that 
should  make  future  changes  in  the  details  of  the  design  a 
matter  of  orderly  development  and  progressive  improve- 
ment. Curiously  enough,  however,  this  freedom  of  action 
must  later  give  way  to  its  exact  opposite.  Once  the  design 
is  completed  and  manufacturing  started,  the  designer  must 
"sit  tight." 

Usually  the  production  man  himself  is  alive  to  the 
serious  delays  and  losses  caused  by  changes  in  design  made 
after  production  has  begun;  but  ordinarily  the  changes 
originate  from  a  source  outside  of  the  shops.  Improve- 
ments in  design  are  rapid,  and  the  temptation  is  great  to 
make  changes  that  better,  or  seem  to  better,  the  product. 
Consequently  after  all  the  trouble  of  getting  out  carefully 
detailed  plans,  after  making  manufacturing  arrangements 
to  carry  them  out,  and  even  after  material  is  in  process,  a 
rumor  comes  into  the  shop  that  such  and  such  a  thing  is  to 
be  changed.  The  result  is  uncertainty  and  the  beginning  of 
confusion.  Then  comes  the  order  for  the  change,  which  is 
usually  made  without  the  degree  of  care  that  was  used  in 
presenting  the  original  design,  for  as  soon  as  the  making  of 
changes  begins,  many  ill-considered  changes  are  suggested. 
The  general  effect,  then,  is  to  mix  experimental  work  with 
production,  instead  of  separating  it  out  of  the  routine  manu- 
facturing shops  as  is  done  in  any  well-regulated  factory. 

When  Improvement  Changes  Should  Be  Made 

Some  years  ago  in  a  large  plant  making  a  high-grade  car, 
changes  in  design  were  being  made  with  such  frequency  that 


244  THE  CONTROL  OF  QUALITY 

the  effect  on  production  finally  demanded  the  installation  of 
a  special  system  for  handling  these  changes.  It  is  true  that 
the  art  was  moving  forward  with  rapid  strides.  Without 
doubt  business  considerations  warranted  the  prompt  adop- 
tion of  some  of  the  new  improvements.  On  the  other  hand, 
the  model  was  changed  formally  each  year,  and  most  of  the 
improvements  should  have  been  collected  systematically 
and  saved  for  incorporation  in  the  next  season's  car.  The 
chief  engineer,  however,  was  busy  improving  the  car  from 
day  to  day,  while  the  factory  output  was  unnecessarily 
slowed  down  and  the  work  made  much  more  costly  to  the 
purchasing  public. 

It  is  frequently  a  matter  of  considerable  doubt  whether  a 
radical  change  in  appearance  is  advisable,  even  when  the 
change  is  made  for  the  ostensible  purpose  of  modernizing 
the  design.  A  ''quality"  article,  for  example,  has  been 
developed  in  accordance  with  an  ideal — otherwise  it  would 
not  be  high  grade.  In  the  course  of  time,  it  acquires  in  the 
eyes  of  its  friends  a  distinctive  but  often  intangible  some- 
thing which  makes  it  different  and  gives  it  a  distinctive 
character.  The  time  inevitably  comes  when  there  is  a 
temptation  to  bring  the  design  up  to  date,  but  long  before 
the  attempt  is  made,  the  necessary  changes  should  be 
mapped  out  along  lines  consistent  with  the  basic  ideal  of  the 
design.  Then  the  product  can  be  modernized  gradually 
without  losing  the  resemblance  to  the  original  which  is  as- 
sociated with  a  reputation  for  satisfaction.  The  ideal  on 
which  the  design  was  made  and  on  which  the  success  of  the 
business  is  founded  should  never  be  destroyed. 

Every  Cause  Has  Several  Effects 

Some  changes  must  be  made.  In  such  cases  the  greatest 
care  and  attention  should  be  applied  to  see  that  they  are 
put  into  effect  so  gradually  as  not  to  interfere  with  efficient 


QUALITY  DEFINED— THE  IDEAL  STANDARD  245 

production  any  more  than  is  absolutely  necessary.  It  be- 
comes the  duty  of  the  production  man  to  impress  that  fact 
strongly  upon  the  designer.  Very  often  the  fact  alone  must 
be  accepted,  because  the  sources  of  loss  are  so  intimately 
interwoven  with  the  processes  of  production  that  separating 
them  out  is  too  difficult  to  be  worth  while.  It  is  a  perfectly 
safe  statement  that  any  change  costs  money  in  an  amount 
entirely  out  of  all  proportion  to  the  direct  work  involved. 

Finally,  there  comes  to  mind  the  principle  laid  down  by 
Herbert  Spencer—  "  Every  cause  has  more  than  one  effect." 
You  may  accomplish  a  slight  local  improvement,  but  you 
should  not  forget  that  you  have  altered  other  conditions  as 
well.  The  very  thing  that  improves  one  part  of  the  design 
may  affect  other  parts  adversely. 

Precautions  to  Avoid  Changes 

Changes  in  work  due  to  errors  in  design  are  almost  bound 
to  occur,  but  every  effort  should  be  made  to  minimize  them. 
Careful  work  in  the  drafting-room  will  decrease  such  errors. 
In  small  accurate  work  it  is  often  helpful  to  make  drawings 
to  a  magnified  scale,  or  even  to  make  a  large-scale  model. 
Many  engineers  hold  that  our  drafting-room  practice  has 
reached  "such  a  degree  of  perfection  that  the  making  of  a 
model  is  unnecessary.  There  are  some  cases,  however,  in 
which  a  model  would  seem  to  be  advisable,  if  for  no  other 
reason  than  to  assist  the  draftsman's  eye  to  a  more  readily 
comprehended  picture  of  the  relations  of  the  component 
parts  in  a  complicated  assembly. 

Further,  in  every  sort  of  work  which  permits  of  making  a 
model  or  sample,  it  should  be  noted  that  every  practicable 
effort  should  be  made  to  avoid  changes  occasioned  by  mis- 
takes in  the  designs,  by  the  obvious  process  of  eliminating 
the  necessity  for  such  changes  before  beginning  manufactur- 
ing operations.  The  way  to  discover  and  eliminate  the 


246  THE  CONTROL  OF  QUALITY 


ORDER  FOR  CHANGE  IN  DRAWING 

Operation  Mark Date 

Tool  Name 

Description  of  Change  


ison  for  Change - -. 


Preliminary  Action  by  Order  Dept.  on  Outstanding  Orders 

Final  Action  by  Order  Dept.  (taken  after  completion  of  change) 


Drafting  Room  to  check  details  of  other  tools  that  may  be  affected 
by  the  above. 

Suggested  by  Approved      PWOCH8 IN01NIM 

Classification  of  Change Accepted 

PRODUCTION  ENGINEER 


Copies  to 

Process  Engineer. 
Chief  Draftsman. 
Order  Superintendent. 


Figure  57.     Order  for  Change  in  Drawing 
Form  used  at  Remington  armory,  Bridgeport. 


QUALITY  DEFINED— THE  IDEAL  STANDARD  247 

' '  bugs  "  in  a  new  design  of  product  is  by  careful  and  thorough 
work  in  the  experimental  and  research  department.  The 
latter  department  will  pay  for  itself  many  times  over  by 
providing  a  smooth  path  of  development  and  co-ordination 
between  the  engineering  department  and  the  producing 
shops.  Without  this  procedure,  experimental  work,  which 
has  to  be  done  somewhere  by  someone  in  any  case,  is 
mixed  with  production,  and  the  resulting  great  waste  is 
quite  likely  to  be  lost  sight  of  because  no  ordinary  cost  or 
production  system  will  reveal  it. 


CHAPTER  XV 
THE  WORKING  STANDARDS 

The  Compromise  in  Setting  Tolerances 

Granted  that  the  ideal  standard  cannot  be  realized  in 
practice  because  quality  varies  continually,  practical  manu- 
facturing or  working  standards  must  be  determined.  These 
vary  from  the  ideal  standard  by  certain  differences  or  allowed 
errors,  and  by  adding  them  to  the  outline  design  or  ideal 
standard,  a  complete  design  is  obtained. 

The  use  of  the  plural  in  referring  to  the  working  stand- 
ards is  intentional,  since  many  differences  from  the  ideal 
design  will  occur  in  the  shops,  and  from  these  must  be  se- 
lected the  variations  that  are  to  be  allowed  in  the  finished 
article.  This  process  of  selection  will  fix  the  working  stand- 
ards. Needless  to  say,  the  determination  of  permissible 
errors  or  variations  is  not  always  a  simple  matter,  but  rather 
a  task  calling  for  the  exercise  of  unusual  discrimination  and 
good  judgment.  The  designer,  especially  when  freed  from 
responsibility  for  costs,  will  endeavor  to  have  these  varia- 
tions as  small  as  possible.  He  will  insist  on  a  close  approxi- 
mation to  the  ideal.  On  the  other  hand,  the  man  who  is 
responsible  for  production  will  reason  that  the  time  and 
cost  of  manufacturing  under  certain  conditions  will  increase 
with  the  degree  of  accuracy  required;  so  he  naturally  will 
seek  to  obtain  the  largest  possible  allowed  errors. 

If  the  situation  is  dominated  by  either  of  the  above- 
mentioned  views,  trouble  is  very  likely  to  ensue.  The  unre- 
stricted designer  usually  demands  unnecessarily  high  stand- 
ards, government  work  sometimes  furnishing  an  extreme 
example.  Contrariwise,  the  unrestricted  production  man 

248 


THE  WORKING  STANDARDS  249 

usually  tends  too  strongly  in  the  opposite  direction.  As  is 
usual  in  such  cases,  the  truth  lies  somewhere  between  the 
two  extremes;  hence  the  necessity  for  someone  to  apply 
good  common  sense  in  the  selection  of  the  working  stand- 
ards. The  best  compromise  is  to  be  had,  usually,  when  the 
standards  are  selected  by  a  well-balanced  committee  on 
which  engineering,  production,  and  inspection  are  repre- 
sented. 

Raw  Material  Standards 

The  design  states  the  kind  of  material  from  which  a  part 
is  to  be  made,  and  specifies  the  required  conditioning  of  the 
material  (such,  for  instance,  as  heat  treatment),  also  the 
dimensions  and  form  desired,  the  finish  of  the  surface,  and 
frequently  the  requirements  to  be  met  in  assembling  and 
functioning  in  service. 

The  selection  of  suitable  raw  material  is  a  matter  of  the 
utmost  importance,  in  which  the  governing  considerations 
are  uniformity,  ability  to  meet  service  requirements,  and 
ease  of  working  in  the  manufacturing  process.  First  cost  is 
a  subordinate  consideration  in  nearly  every  case,  in  com- 
parison with  uniform  behavior  in  manufacturing  and  uni- 
form performance  under  working  loads.  A  typical  instance 
is  furnished  by  the  motor  industry,  where  a  very  low-priced 
car  has  been  built  of  the  highest  percentage  of  alloy  steels. 
There  are  better  places  for  economy  than  in  the  raw 
materials. 

The  determination  of  working  standards  for  raw  ma- 
terial has  received  a  great  deal  of  attention  in  recent  years 
and  need  not  be  dwelt  upon  here.  The  preparation  of 
standard  specifications  for  various  kinds  of  material  (and 
for  the  different  grades  of  each  kind)  by  some  of  the  great 
railroads  and  manufacturing  plants,  by  various  governmen- 
tal departments,  and  by  the  American  Society  for  Testing 


250  THE  CONTROL  OF  QUALITY 

Materials,  has  made  available  a  large  body  of  technical 
data  arranged  in  systematic  form.  It  is  only  necessary  to 
select  the  specifications  of  a  suitable  material  in  order  to 
have  the  limiting  conditions  known. 

In  the  case  of  metals,  especially,  the  data  are  quite  com- 
plete. The  permissible  variations  in  the  chemical  constit- 
uents are  set  forth,  together  with  the  limiting  conditions 
for  pertinent  physical  characteristics.  In  the  case  of  other 
kinds  of  material,  the  essential  characteristics  are  mentioned 
and  limits  frequently  stated.  It  would  seem,  however,  that 
much  progress  remains  to  be  made  in  specifications  for  many 
of  the  usual  non-metallic  materials,  such  as  wood  and  fibrous 
materials,  principally  in  the  way  of  information  to  be 
collected  and  systematized  through  the  application  of  the 
microscope  and  the  binocular  microscope  and  other  scien- 
tific apparatus  not  applied  as  yet  to  any  great  extent  in  such 
work.  The  use  of  micro-photography  in  the  metallographic 
study  of  metals  has  developed  a  wide  and  fruitful  field.  A 
similar  development  will  follow  the  application  of  these 
methods  to  many  of  the  non-metals. 

Conditioning  Standards 

The  determination  of  working  standards  for  what,  for 
lack  of  a  better  term,  may  be  called  the  "conditioning  of 
material"  is  not  so  simple  a  matter.  A  part  made  from 
soft  or  untreated  steel  in  order  to  permit  economical  ma- 
chining or  working,  subsequently  may  require  some  form 
of  hardening  or  tempering  in  order  to  suit  it  to  the  duty  it 
must  perform  in  the  assembled  mechanism.  In  fixing  the 
limiting  conditions  the  scleroscope  or  Brinnell  test  is 
available,  or  perhaps  a  file  test  may  answer.  Another  ele- 
ment is  introduced,  however,  if  appreciable  distortion 
occurs  in  individual  parts  to  such  an  extent  as  to  require 
straightening.  If  straightening  is  necessary  and  the  func- 


THE  WORKING  STANDARDS  251 

tion  of  the  component  part  is  an  important  one,  some  sort 
of  special  test  should  be  specified,  of  a  kind  to  demonstrate 
that  the  part  will  pass  the  maximum  demands  that  are  likely 
to  be  encountered  in  service. 

Important  springs  should  have  maximum  and  minimum 
weighing  tests  to  be  made  in  a  special  fixture,  and  should  be 
set  up  for  a  specified  period  of  time  and  to  a  given  displace- 
ment without  more  than  an  allowed  set. 

The  time  and  order  or  the  particular  stage  of  manufac- 
ture at  which  any  such  special  tests  should  be  applied  may 
possibly  be  of  importance,  hence  the  value  of  listing  these 
tests  on  operation  sheets  and  route  cards,  just  as  if  they 
were  ordinary  manufacturing  operations.  Special  tests 
should  be  provided  for  important  non-metallic  materials 
requiring  special  treatment  or  conditioning  prior  to  or  dur- 
ing manufacture.  The  kiln  drying  of  high-grade  lumber  is 
a  case  in  point,  where  the  binocular  microscope  may  some- 
times be  used  to  advantage. 

Standards  of  Finish 

There  is  considerable  laxity  in  determining  standards  for 
exterior  finish.  Probably  the  fact  that  more  attention  is 
not  devoted  to  setting  standards  of  finish  is  due  as  much  to 
commercial  considerations  as  to  the  difficulty  of  reducing 
the  degree  of  finish  to  measurable  and  tangible  terms.  The 
manufacturer  selects  a  finishing  process  sufficiently  econom- 
ical for  the  purpose,  and  then  strives  to  get  as  good  a  finish 
with  that  process  as  is  reasonably  possible,  on  the  general 
assumption  that  the  shinier  or  prettier  an  article  looks  the 
more  it  will  appeal  to  the  customer's  eye.  Unfortunately 
there  often  is  good  reason  for  this  attitude,  many  purchasers 
prefering  a  polished  surface  where  a  good  coat  of  paint  over 
a  rough  surface  would  be  more  durable  and  less  expensive  to 
maintain.  In  competitive  businesses,  however,  it  is  often 


252  THE  CONTROL  OF  QUALITY 

wise  to  give  the  purchaser  what  he  thinks  he  wants,  even  if  it 
may  not  be  the  best  thing  for  him.  Note,  for  example,  the 
face  of  a  pressure  valve  flange.  It  has  been  faced  off  in 
the  lathe  with  a  roughing  cut,  followed  by  at  least  one  finish- 
ing cut.  Then  one  or  two  small  circular  grooves  are  cut  for 
the  gasket  to  be  squeezed  into,  in  order,  to  secure  tightness. 
And  yet  one  rough  turned  facing  would  accomplish  the  pur- 
pose better  by  providing  a  multitude  of  grooves.  This  is 
only  another  instance  of  perpetuating  the  errors  of  the  past 
by  thoughtless  imitation. 

Oftentimes  the  allowable  gradations  in  the  hue,  shade, 
or  tint  desired  for  a  colored  surface  are  left  to  the  judgment 
of  the  production  man  or  the  inspector.  Sometimes  a  sam- 
ple is  furnished  which  is  to  be  approximated  as  nearly  as 
possible  commercially.  In  such  cases,  it  is  well  to  obtain 
the  advantage  of  manufacturing  to  limits  by  providing 
samples  showing  all  extremes  that  will  be  allowed.  When 
standards  for  smoothness  of  finish  are  to  be  set,  the  same 
practice  should  be  followed,  i.e.,  the  use  of  standard  samples. 
Preferably  a  few  sample  parts  should  be  used  for  small  work, 
some  showing/acceptable  work,  and  others  showing  work  not 
quite  good  enough  to  be  passed.  In  other  words,  the  sam- 
ples should  be  selected  close  to  the  limiting  conditions 
desired.  This  general  process  is  the  best  that  can  be 
adopted  until  more  and  more  of  such  qualities  are  reduced 
to  a  basis  of  numerical  measurement — a  result  that  is  sure 
to  come  as  the  qualitative  refinement  of  our  industries 
progresses. 

Standards  of  Dimension  and  Form 

In  its  ultimate  effect  the  establishment  of  practical  or 
working  standards  for  dimension  and  form  covers  the  most 
important  and  far-reaching  subject  of  all.  It  is  of  the  es- 
sence of  that  great  branch  of  repetition  work  which  is  known 


THE  WORKING  STANDARDS 


253 


254  THE  CONTROL  OF  QUALITY 

as  "interchangeable  manufacturing,"  which  will  be  consid- 
ered in  greater  detail  in  the  following  chapter. 

In  determining  the  working  standards  for  dimension  and 
form  or  shape,  the  relation  of  each  part  to  the  other  com- 
ponent parts  of  the  mechanism  must  first  be  considered. 
The  ideal  standard,  as  described  in  the  preceding  discussion, 
fixes  one  size  and  shape,  and  it  may  be  assumed  that  the 
designer  in  articulating  the  mechanical  movements  involved 
provided  for  the  necessary  strength  and  other  physical 
qualities  required.  These  qualities  have  to  do  with  what 
might  be  termed  the  "main  body"  or  "interior"  of  the 
parts,  whereas  for  present  purposes  we  are  concerned  with 
variations  in  the  outer  surfaces  or  exterior  of  a  given  part, 
with  special  reference  to  the  similar  surfaces  of  the  other 
parts  of  the  mechanism  with  which  the  given  part  works. 
We  know  that  these  outer  ends  of  the  dimensions,  so  to 
speak,  are  going  to  vary,  and  therefore  we  must  determine 
the  limiting  variations  in  the  fit  of  the  one  part  to  the 
other  parts  that  will  still  secure  a  proper  functioning  of  the 
entire  mechanism.  In  this  way  we  can  settle  upon  the 
greatest  distance  from  edge  to  edge  of  related  parts,  as  well  as 
the  smallest  separation  or  play  that  is  permissible,  thus  de- 
termining the  maximum  and  the  minimum  allowance  for  fit. 

With  the  figures  just  referred  to  as  a  guide,  the  next 
step  involves  the  determination  of  the  permissible  variations 
in  the  dimensions  of  each  part,  considered  separately,  and 
these  maximum  permissible  variations  fix  the  limits  of  the 
dimensions,  the  difference  between  any  set  of  limits  being 
known  as  the  "tolerance." 

Allowed  Variations  Defined 

The  terms  "allowance,"  "tolerance,"  and  "limits" 
have  long  been  a  part  of  the  technical  nomenclature  of 
repetition  and  interchangeable  manufacture,  but  are  only 


THE  WORKING  STANDARDS  255 

recently  beginning  to  receive  the  detailed  study  they  merit. 
It  is  not  the  purpose  of  this  book,  however,  to  do  more  than 
trace  their  application  in  the  development  of  working  stand- 
ards of  dimension,  as  a  resultant  of  the  basic  idea  that 
quality  is  a  variable.1 

The  following  definitions  are  taken  from  the  "Progress 
Report  of  the  Committee  on  Limits  and  Tolerances  in 
Screw  Thread  Fits,  to  the  Council  of  the  American  Society 
of  Mechanical  Engineers,"  as  published  in  the  Journal  of 
that  Society  for  August,  1918: 

Allowance — Variation  in  dimensions  to  allow  for  different 
qualities  of  fit. 

Tolerance — The  allowable  variation  in  size  equal  to  the  dif- 
ference between  the  minimum  and  maximum  limits. 

Limits — Two  sizes  expressed  by  positive  dimensions,  the 
larger  being  termed  the  maximum,  and  the  smaller,  the  minimum 
limit. 

In  some  cases,  as  in  mating  threaded  parts,  or  in  moving 
parts  which  must  not  touch  each  other  (such  as  in  turbines, 
pumps,  and  so  on),  an  actual  clearance  must  be  provided 
for. 

Clearance — A  difference  in  dimensions,  or  in  the  shape  of  the 

surface,  prescribed  in  order  that  two  surfaces,  or  parts  of  surfaces 

may  be  clear  of  one  another.2 

The  opposite  situation  arises  in  certain  cases,  when  parts 
are  fitted  with  a  "pinch." 

Necessary  Precautions 

The  process  of  working  from  the  allowance  to  the 
determination  of  tolerances  and  limits  involves  a  nice  ap- 
plication of  judgment  (both  to  the  theory  of  the  design  and 

1  For  an  interesting  discussion  of  this  subject  the  reader  is  referred  to  a  paper  on  "  Gage  Limits 
in  Interchangeable  Manufacture,"  by  Colonel  E.  C.  Peck  in  the  October,  1919,  issue  of  Mechani- 
cal Engineering;  also  to  some  notes  on  the  "Theory  of  Tolerances  and  Comparison  of  Symmetri- 
cal and  Asymmetrical  Systems,"  (Ibid.,  July,  1919),  together  with  a  very  practical  comment 
thereon  by  J.  Airey  (Ibid.,  October,  1919). 

2  British  Engineering  Standards  Association  definition. 


256  THE  CONTROL  OF  QUALITY 

to  the  current  shop  processes),  which  should  consider  es- 
pecially the  following: 

1.  The  effect  on  the  allowance  for  one  dimension,  of  the 
errors  accumulated  from  the  variations  in  dimension  of  any 
other  mating  part  or  bearing  point,  if  any.     For  example, 
if  we  are  determining  permissible  variations  in  the  diameters 
of  two  mating  gear-wheels,  we  must  consider  the  effect  of 
the  play  to  be  allowed  in  their  supporting  bearings. 

2.  The  effect  of  wear  of  the  parts  after  the  mechanism  is 
in  use  in  service.     The  tolerances  should  be  proportioned  to 
favor  the  parts  that  probably  will  wear  most  rapidly,  with 
the  object  in  view  of  insuring  uniform  and  even  wear. 

3.  The  relative  difficulty  of  manufacturing  the  parts  con- 
cerned.    The  parts  should  be  favored  whose  manufacture 
involves  the  use  of  mechanical  operations  or  processes  that 
are  the  most  difficult  to  hold  to  dimensional  accuracy. 

4.  The  effect  of  wear  of  cutting  tools,  dies,  fixtures,  jigs, 
gages,  or  other  special  manufacturing  equipment,  in  order 
to  secure  the  greatest  economy  in  their  cost.     The  most  ex- 
pensive equipment  should  be  given  the  longest  wearing  life. 

The  above  process  will  give  a  set  of  limits  for  all  im- 
portant dimensions  of  the  finished  parts  only,  so  that  a  proc- 
ess, somewhat  similar  in  principle,  must  be  gone  through 
with  to  determine  similar  limits  for  the  vital  dimensions  of 
unfinished  parts  after  each  mechanical  operation  involved  in 
the  process  of  manufacture. 

If  "  close  work,"  requiring  a  high  quality  of  dimensional 
accuracy,  is  involved,  it  is  specially  important  to  consider 
the  possible  effects  of  errors  accumulated  from  process  to 
process.  This  suggests,  at  once,  the  importance  of  a  well- 
worked-out  list  of  mechanical  processes  to  be  used  in  making 
any  given  part,  which  list  should  show  not  only  the  sequence 
in  which  the  work  will  be  processed  ordinarily,  but  also  the 
alternative  arrangements  of  operations  that  may  be  used  in 


THE  WORKING  STANDARDS 


257 


Figure  59.     Reading  Inside  Micrometers  after  Measuring  Inside  of  Cylinder 
Brown  and  Sharpe  Manufacturing  Company. 


17 


258  THE  CONTROL  OF  QUALITY 

case  shop  exigencies  indicate  the  desirability  of  rearranged 
routings.  In  this  way  we  are  enabled  to  foresee  what  ac- 
cumulated errors  may  arise  in  the  case  of  emergency  changes 
in  routing,  and,  being  forewarned,  to  guard  against  them. 

The  selection  of  locating  and  reference  points  is  closely 
inter-related  with  the  above.  Working  from  holes  provides 
a  safe  method  when  too  much  wear  is  not  involved.  The 
same  scheme  may  often  be  simulated  by  the  use  of  tempo- 
rary holes  or  by  adding  locating  lugs  which  are  cut  away  after 
they  have  served  their  purpose. 

It  is  sometimes  desirable  to  minimize  the  effect  of  ac- 
cumulated errors  by  distributing  them — a  procedure  known 
in  precision  of  measurement  as  "solving  the  problem  for 
equal  effects,"  i.e.,  the  errors  allowed  in  each  variable  are 
calculated  to  give  the  same  effect  in  the  final  answer. 

Dimensional  Working  Standards 

After  the  limits  have  been  worked  out,  they  should  be 
shown  as  a  part  of  the  working  drawings.  If  these  draw- 
ings are  then  furnished  to  the  shops  as  the  final  references 
for  production  purposes,  they  become  the  practical  working 
standards  for  dimension,  as  the  term  is  used  herein.  With 
highly  skilled  operators,  working  on  processes  inherently  ac- 
curate, these  plans  may  be  all  that  is  necessary.  Where  a 
relatively  small  number  of  parts  are  to  be  made,  and  es- 
pecially in  large  work,  it  would  not  be  the  part  of  good  sense 
to  supply  the  shops  with  anything  in  addition  to  the  plans 
as  the  standards.  In  many  cases  all  the  information 
required  may  be  set  forth  on  the  working  drawing  for  the 
finished  part,  including  both  the  limits  for  the  finished  work 
and  the  amounts  of  stock  to  be  allowed  for  grinding, 
turning,  and  similar  operations. 

In  passing  from  the  classes  of  work  just  indicated,  to  the 
quantity  production  of  interchangeable  parts  of  small  size, 


THE  WORKING  STANDARDS  259 

we  enter  a  field  where  economy  of  manufacturing  indicates 
the  desirability  of  increasingly  specialized  equipment,  such 
as  special  cutting  tools,  holding  devices,  and  gages.  In  such 
cases  if  working  plans  are  supplied  to  the  shops  at  all,  it 
usually  is  best  to  do  so  only  as  a  matter  of  information  and 
to  substitute  for  adjustable  precision  measuring  instru- 
ments fixed-dimension  gages  of  various  sorts  which  have  the 
limiting  dimensions  worked  into  them  in  physical  form. 

It  is  safe  to  say  that  the  next  few  years  will  see  a  great 
extension  of  the  use  of  limit  gages  in  American  factories, 
with  corresponding  benefits  as  regards  both  quality  and 
economy.  The  introduction  of  a  gaging  system,  however, 
will  cause  new  conditions  to  arise  which  will  involve  special 
problems  peculiar  to  the  system  in  question.  It  is  a  matter 
in  which  some  very  small  things  become  paramount,  and 
hence  require  the  most  careful  and  systematic  attention,  as 
will  be  discussed  in  a  later  chapter.  For  the  present,  at- 
tention is  invited  to  the  fact  that  when  gages  are  used,  as 
just  stated,  they  constitute  the  working  standards,  and  the 
plans  cease  to  function  as  the  working  standards. 

It  remains  to  be  said,  for  completeness,  that  it  may  not 
be  considered  desirable  in  certain  cases  to  incorporate,  in 
the  gages  as  furnished  to  the  shops,  the  maximum  limits 
that  may  be  used  while  still  assuring  proper  functioning  of 
the  parts  after  their  assembly  into  the  mechanism.  This 
practice  of  making  the  shops  work  to  closer  limits  than  the 
inspectors  are  permitted  to  pass  finds  its  justification  some- 
times in  a  longer  useful  life  for  the  gages.  The  practice, 
however,  rests  chiefly  on  the  idea  that  it  may  help  to  reduce 
the  losses  in  spoiled  work  by  permitting  the  salvage  of 
some  of  the  parts  that  are  bound  to  fall  outside  of  the  limits 
given  to  the  factory,  while  also  encouraging  the  cultivation 
of  greater  accuracy  in  the  operators.  This  savors  somewhat 
of  the  theory  of  the  traffic  laws  that  have  given  rise  to  signs 


260 


THE  CONTROL  OF  QUALITY 


THE  WORKING  STANDARDS  261 

reading  "Speed  limit  15  miles,"  which  one  so  often  sees  out- 
side small  towns.  The  sign  probably  is  put  there  in  the 
hope  that  the  motorist  will  reduce  his  speed  to  25  or  perhaps 
20  miles,  depending  on  the  degree  of  hopefulness  of  the 
authorities,  but  usually  he  keeps  his  foot  on  the  accelerator. 
Now  the  machine  operator  will  answer  to  the  same  psy- 
chological reactions  if  he  knows  there  are  two  standards  in 
use,  unless  and  only  in  case  conditions  are  so  arranged  that 
he  is  made  to  realize  it  as  being  to  his  best  interest  to  stick 
to  the  limits  given  him.  It  may  be  necessary,  in  fact,  to 
keep  the  larger  limits  a  secret,  which  involves  using  them  in 
a  separate  salvage  department.  As  a  rule,  however,  it 
would  seem  to  be  better  practice,  with  the  possible  excep- 
tion of  certain  very  special  cases,  to  try  for  the  same  result 
by  the  more  direct  route  of  frankly  making  known  the 
maximum  permissible  variations,  and  then  taking  proper 
precautions  to  safeguard  these  limits. 

Assembling  Standards 

Theoretically,  in  strictly  interchangeable  work  it  should 
not  be  necessary  to  check  up  the  fit  of  parts  after  they  have 
been  assembled,  except  possibly  as  an  additional  assurance 
that  the  constituent  parts  of  the  assembly  are  within  the 
allowed  tolerances.  As  a  practical  proposition,  however,  it 
is  often  advisable  to  provide  for  the  verification  of  certain 
important  functioning  dimensions  in  subassemblies,  as, 
for  example,  when  parts  are  assembled  on  a  tapering  shaft, 
or  where  the  effect  of  improper  fits  is  multiplied  by  a  long 
arm  (as  in  the  case  of  a  long  rod  with  a  short  bearing  on  one 
end,  working  under  conditions  that  make  side  play  of  the 
other  end  of  the  rod  undesirable) .  In  work  made  partially 
interchangeable,  such  assembling  standards  should  be  pro- 
vided for,  by  setting  limiting  dimensions  for  the  assembled 
parts  in  the  case  of  all  vital  dimensions. 


262  THE  CONTROL  OF  QUALITY 

Final  Tests 

After  the  parts  of  the  mechanism  have  been  assembled, 
a  final  test,  or  series  of  tests,  should  be  made,  simulating  the 
maximum  demands  to  be  made  on  the  mechanism  after  it  is 
placed  in  service.  Strength  tests  are,  in  themselves,  the 
maximum  limit — an  armature  will  spin  at  twice  its  rated 
speed  without  bursting,  or  it  will  not;  a  derrick  will  lift  the 
specified  overload  without  permanent  set,  or  it  will  not;  a 
gun  barrel  will  stand  a  heavy  proof  charge  without  bursting 
or  bulging,  or  it  will  not.  Thus,  in  such  tests  there  is  but 
one  limit.  But,  in  many  of  the  final  tests  and  trials  used  to 
demonstrate  standards  of  quality,  the  same  idea  of  permis- 
sible variations  in  quality  (expressed  in  terms  of  limits)  finds 
application,  whether  these  tests  are  to  be  applied  to  the 
complete  assembly  or  to  some  subassembly.  In  the  testing 
of  the  trigger  pull  of  a  rifle,  for  example,  the  limits  may  be 
set  at  given  minimum  and  maximum  pulls  stated  in  pounds ; 
or  the  economy  and  the  speed  regulation  of  a  motor  may  be 
demonstrated  by  trial  to  be  within  certain  limiting  per- 
centages. 

Final  tests  must  be  made  under  as  nearly  the  same  con- 
ditions as  the  mechanism  will  encounter  in  service  when 
reasonably  possible.  If  this  cannot  be  done,  the  test  con- 
ditions should  always  vary  from  service  conditions  in  a 
known  way  and  to  the  same  degree,  i.e.,  all  mechanisms 
should  be  tested  under  like  conditions. 

Recapitulation 

Working  from  the  theory  that  quality  is  a  variable,  and 
hence  that  the  ideal  standard  or  design  cannot  be  reproduced 
exactly,  the  conclusion  is  reached  that  practical  working 
standards  should  be  supplied  to  the  factory  in  form  to  indi- 
cate the  limits  within  which  it  is  desired  to  have  the  work 
made.  These  practical  standards  should  cover  the  various 


THE  WORKING  STANDARDS  263 

matters  affecting  quality,  such  as  dimension,  finish,  and 
so  forth;  and  all  should  be  formulated  with  a  reasonable 
mental  attitude  that  makes  provision  for  variations,  because 
they  are  bound  to  occur.  With  this  clearly  understood,  we 
are  in  a  position  to  take  up  the  consideration  of  the  steps 
necessary  to  secure  results  in  the  factory  as  nearly  as  may 
be  in  accordance  with  the  standards  of  quality  desired,  it 
being  noted  in  this  connection  that  the  above  principles 
apply  regardless  of  what  the  product  of  the  manufactur- 
ing operations  may  be.  Metal  work  has  been  used 
merely  because  it  is  more  inclusive  and  complete  as  an 
illustration. 


CHAPTER  XVI 
REPETITION  MANUFACTURING 

Uniformity  for  Economy 

The  thought  of  quality  as  something  that  is  continually 
shifting  and  varying,  when  translated  into  form  for  use  in 
the  factory,  gives  rise,  among  other  things,  to  the  whole 
subject  of  tolerances  and  limits.  Thus  it  becomes  ap- 
parent that  no  design  is  sufficiently  complete  for  intelligent 
manufacturing  purposes  unless  the  limits  for  each  and  every 
governing  characteristic  are  known.  Furthermore,  just  as 
a  clear  appreciation  of  this  idea  of  variations  is  essential  in 
repetitive  work,  so  also  is  it  desirable  that  the  principles  of 
repetition  manufacturing  be  understood. 

True  manufacturing  involves  making  a  quantity  of  the 
same  article,  uniform  within  limits.  In  this  respect  it  is  the 
diametrical  opposite  of  art  work.  The  manufacturer  seeks 
to  make  things  alike,  but  the  artist  strives  for  the  creation 
of  things  that  are  different  and  individualistic.  The  first 
system  is  far  less  costly;  and  therein  lies  the  real  value  of 
manufacturing,  because  its  product  is  thereby  made  more 
generally  accessible  to  mankind.  We  make  things  alike 
because  it  is  cheaper  rather  than  for  the  sake  of  having  them 
alike,  although  many  secondary  advantages  accrue  from 
this  property  of  uniformity.  In  fact,  it  is  so  very  much 
cheaper  to  make  things  alike  that  the  manufacturer  can 
afford  to  incur  very  heavy  expenditures  in  preparation  alone 
—merely  for  getting  ready  to  manufacture.  Because  he 
does  incur  this  heavy  initial  expense,  and  because  all  his 
later  operations  are  more  or  less  fixed  and  governed  by  these 
preliminary  arrangements,  it  becomes  of  serious  importance 
for  him  to  make  them  correctly  in  the  first  place. 

264 


REPETITION  MANUFACTURING  265 

Uniformity  of  Product  Means  Uniformity  Throughout  Production 
In  making  these  preliminary  arrangements  the  manufac- 
turer must  not  consider  the  preparatory  work  in  a  general 
way  as  affecting  the  finished  product,  but  rather  in  its  rela- 
tion to,  and  effect  on,  each  individual  process.  This  raises 
a  point  that  is  frequently  lost  sight  of  in  repetition  manu- 
facturing, namely,  the  continuous  manufacture  of  one  product 
of  uniform  and  standardized  quality  implies  an  equal  uniform- 
ity and  standardization  at  all  stages  of  its  production.  Why? 
Because  it  is  cheaper  to  manufacture  in  this  way,  and  it  is 
cheaper  to  manufacture  in  this  way  because  large  errors  in 
the  earlier  stages  of  the  work  require  correction  later  on, 
when  it  is  not  so  simple  to  bring  the  work  into  line.  Con- 
sequently each  component  process  should  be  considered  as  a 
separate  production  point  for  the  continuous  manufacture 
of  uniform  quality.  If  one  process  is  left  as  a  loophole  for 
large  variations  to  enter,  throughout  the  remaining  processes 
a  constant  struggle  must  be  engaged  in  to  correct  them. 
Obviously,  this  attention  to  uniform  quality  must  be  ex- 
tended to  include  the  raw  material  itself,  clear  back  to  the 
original  source  of  supply. 

It  will  prove  useful  in  what  follows  to  note  incidentally 
that  excessive  variations  in  the  finished  product  mean  simply 
that  there  are  variations  in  the  earlier  processes.  For  differ- 
ences in  the  completed  articles  are  the  algebraic  sum  of  the 
errors  made  in  all  of  the  earlier  manufacturing  processes. 
Noting  for  the  moment  that  interchangeable  manu- 
facturing is  only  one  of  the  several  classes  of  repetition 
work,  let  us  now  use  it  as  a  specific  example  in  studying 
some  of  the  interesting  phenomena  of  such  work. 

Interchangeable  Manufacturing 

I  have  before  me  an  Ingersoll  watch  of  the  Reliance 
model,  also  an  Eversharp  pencil.     Both  are  products  of 


266  THE  CONTROL  OF  QUALITY 

standard  quality  and  must  be  made  by  the  methods  of  inter- 
changeable manufacturing.  In  other  words,  the  attempt 
is  made,  in  manufacturing  a  quantity  of  any  one  of  the  com- 
ponent parts,  to  make  all  of  these  individual  parts  so  nearly 
alike  that  any  one  of  them  may  be  used  in  the  assembled 
mechanism  with  the  assurance  of  subsequent  successful 
functioning.  Except  for  the  crystal,  the  springs,  and  per- 
haps one  or  two  minor  parts  of  the  watch,  there  is  no  special 
object  in  having  any  of  the  parts  interchangeable  after  the 
mechanism  has  been  sold  and  placed  in  use,  as  there  is  little 
likelihood  of  any  of  them  having  to  be  replaced.  In  fact, 
if  all  our  mechanisms  could  be  proportioned  and  built  as 
perfectly  as  the  "wonderful  one-horse  chaise,"  so  that  all 
the  parts  would  wear  evenly  and  all  become  worn  out  at  the 
same  instant  of  time,  the  only  value  of  interchangeability 
of  parts  in  service  would  be  in  the  rather  remote  case  of  an 
accident.  Nevertheless,  there  seems  to  be  a  somewhat 
popular  misconception  that  parts  are  made  interchangeable 
for  the  express  purpose  of  securing  the  possibility  of  replac- 
ing parts,  whereas  the  real  purpose  is  to  secure  certain 
economies  in  manufacture  that  are  possible  only  by  the 
methods  of  interchangeable  manufacturing.  The  inter- 
changeability  of  parts  in  service,  while  often  convenient  and 
frequently  important,  follows  as  a  by-product  quite  second- 
ary in  value  to  the  primary  purpose,  which  is  economical 
production. 

The  Industrial  Revolution 

Now  let  us  see  wherein  making  parts  interchangeable 
decreases  manufacturing  costs.  When  Adam  Smith  wrote 
the  "Wealth  of  Nations"  (1776)  he  described  the  principle 
of  the  division  of  labor  by  citing  the  well-known  example 
of  the  manufacture  of  pins,  pointing  out  that  if  the  work  was 
divided  up  into  several  operations  so  that  one  man  concen- 


REPETITION  MANUFACTURING  267 

trated  on,  say,  heading  pins,  and  so  on  for  each  worker,  the 
number  of  pins  produced  per  man  would  very  greatly  exceed 
the  production  of  any  one  man  making  complete  pins,  with- 
out this  analysis  or  dividing  up  of  the  work.  Thus  there 
results  a  saving  or  conservation  of  the  experience  and  skill 
gained  in  doing  the  same  thing  over  and  over,  and  we  recog- 
nize the  outstanding  feature  of  the  great  change  in  produc- 
tion which  is  known  as  the  " industrial  revolution" — a 
method  that  has  almost  entirely  replaced  the  earlier  house- 
hold and  handicraft  methods  of  manufacturing. 

The  Mechanical  Revolution 

The  application  of  labor-saving  machinery  to  produc- 
tion, known  as  the  "mechanical  revolution,"  is  closely  re- 
lated to  the  industrial  revolution,  because  as  a  very  early 
result  of  the  division  of  the  labor  of  manufacture  into  small 
parts  or  operations,  special  labor-saving  devices  and  ma- 
chines were  developed.  Usually,  in  order  to  apply  such 
devices  effectively,  the  work  obviously  must  come  from  one 
operation  or  mechanical  process  to  the  next  operation  in 
pretty  much  the  same  shape  and  size.  Thus  the  division 
of  labor  involves  making  things  very  nearly  alike,  and  in  so 
doing  makes  it  possible  to  realize  economy  of  effort  through 
the  greater  production  secured.  Furthermore,  the  smaller 
subdivision  of  work  permits  an  unskilled  worker  to  acquire 
quickly  the  skill  necessary  to  accomplish  his  part  of  the 
work.  Incidentally,  the  fact  that  pieces  are  more  nearly 
alike  means  that  substantially  the  same  thing  is  done  to 
each  piece  at  each  stage  of  its  manufacture,  in  order  to  ad- 
vance it  to  the  next  operation.  This  must  be  easier  than 
if  each  piece  required  special  treatment.  Incidentally,  a 
better  quality  of  work  results,  and  quality  tends  to  become 
more  uniform;  and  from  uniformity  marked  commercial 
advantages  accrue. 


268 


THE  CONTROL  OF  QUALITY 


Afterward,  and  when,  as  an  eventual  working  out  of  the 
division  of  labor,  certain  processes  are  combined  in  an  auto- 
matic or  semiautomatic  machine,  of  course  it  becomes  still 


Figure  61.     Height  Gage  Used  with  Johansson  Blocks 

more  necessary  to  have  the  work  more  nearly  exact  to  given 
dimensions  and  shape.  While  the  division  of  labor,  how- 
ever, leads  to  making  parts  alike,  the  parts  do  not  necessarily 
have  to  be  so  much  alike  on  this  account  alone  as  to  permit 


REPETITION  MANUFACTURING  269 

full  interchangeability,  nor  even  such  partial  interchange- 
abilty  as  will  allow  assembling  by  selection  of  parts  that  fit 
each  other  well  enough  to  function  properly. 

Economy  in  Assembling 

The  greatest  economy,  however,  in  making  things  suffi- 
ciently alike  to  be  interchangeable  comes  from  the  possibility 
not  only  of  the  more  rapid  assembling  of  component  parts 
into  the  complete  mechanism,  but  also  of  the  use  of  less 
skilled  labor  for  this  work.  A  workman  of  very  ordinary 
experience  and  skill  can  be  taught  to  assemble  all,  or  a  por- 
tion, of  a  complicated  mechanism,  provided  he  can  use  the 
parts  just  as  they  are  supplied.  If,  on  the  other  hand,  the 
parts  must  be  selected  in  order  to  secure  an  assembly  that 
will  function  properly,  much  more  skill  is  required;  and  if 
fitting  of  parts  in  the  form  of  doing  work  on  them  in  the 
assembling  room  is  necessary,  then  in  all  probability  a  very 
high  order  of  mechanical  skill  and  experience  is  requisite. 
Take  the  watch  for  example.  Like  all  mechanisms  contain- 
ing a  source  of  power,  there  is  a  means  of  regulating  the 
rate  of  power  discharge  of  the  mechanism,  within  limits. 
While  the  limits  may  appear  to  be  narrow,  they  are  great 
enough  to  take  up  the  differences  in  action  due  to  the  dif- 
ferent combinations  resulting  from  assembling  parts  which 
have  been  passed  on  to  the  assembling  rooms  as  within  the 
allowed  variations.  Certainly  such  assembling  is  not  a  very 
serious  undertaking.  But  suppose  the  parts,  or  some  of 
them,  required  additional  treatment  in  order  to  fit  them 
and  adjust  them  into  the  mechanism  in  a  way  to  insure 
proper  working.  What  sort  of  labor  would  be  required 
then,  and  how  long  would  it  take  to  complete  an  assembly? 
Also,  would  the  product  be  improved  by  the  hand-fitting  of 
parts  which  would  be  required? 

A  small  article  like  a  watch  is  not  an  extreme  illustration 


270  THE  CONTROL  OF  QUALITY 

of  this  truth,  as  can  be  seen  very  easily  by  observing  the 
strenuous  work  involved  in  the  regulation  of  inaccurately 
punched  plates  in  a  ship  or  other  steel  structure.  The  work 
required  to  get  the  plates  into  position  for  bolting-up  and 
riveting  is  greatly  in  excess  of  the  effort  required  to  punch 
them  accurately  in  the  first  place;  and  if  the  holes  are 
enough  out  of  alignment  to  require  reaming  to  a  larger  size, 
still  more  unnecessary  labor  is  expended,  extra  sizes  of  rivets 
must  be  kept  on  hand,  and  so  on.  Furthermore,  and  most 
important,  any  such  corrective  process  is  not  the  best 
thing  for  the  structure  itself. 

Naturally  these  same  considerations  govern  in  all  lines 
of  manufacturing.  There  is  a  field,  no  doubt,  for  hand- 
work in  special  and  distinctive  bodies  for  high-grade  motor 
cars,  whereas  hand-work  on  the  parts  of  the  engine  (which 
have  been  machined  already  to  a  high  degree  of  accurate 
conformity  to  the  ideal  standard)  is  not  only  out  of  place 
from  the  standpoint  of  economy,  but  actually  detrimental 
as  well.  It  is  very  rarely  indeed  that  anything  is  improved 
by  tinkering. 

The  Work  of  Simeon  North  and  Eli  Whitney 

It  would  be  rather  interesting  to  know  just  when  and 
why  there  arose  the  present  general  misconception  that 
work  is  made  interchangeable  for  the  simple  purpose  of  re- 
placing parts,  inasmuch  as  the  early  exponents  of  the  system, 
like  Simeon  North,  Eli  Whitney,  and  their  contemporaries, 
certainly  understood  exactly  what  the  principle  of  stand- 
ardization really  meant. 

"Simeon  North — First  Official  Pistol  Maker,"  a  memoir 
by  S.  N.  D.  and  R.  H.  North,  was  published  in  1913.  It  is 
a  most  interesting  contribution  to  our  knowledge  of  the  early 
development  of  interchangeable  manufacturing  in  America. 
This  investigation  has  made  it  quite  evident  that  North,  for 


REPETITION  MANUFACTURING  271 

reasons  of  economy,  lack  of  skilled  men,  and  similar  consider- 
ations, which  had  nothing  to  do  with  interchangeability  for 
its  own  sake,  was  willing  to  incur  heavy  initial  expenditures 
and  delays  in  order  to  achieve  an  ultimately  better  result. 
In  a  letter  to  the  Secretary  of  the  Navy  dated  November 
7,  1808,  he  makes  this  significant  comment: 

I  find  that  by  confining  a  workman  to  one  particular  limb  of  the 
pistol  until  he  has  made  two  thousand,  I  save  at  least  one  quarter  of 
his  labour,  to  what  I  should  provided  I  finishd  them  by  small  quanti- 
ties; and  the  work  will  be  as  much  better  as  it  is  quicker  made. 

His  contract  of  April  16,  1813,  with  the  United  States, 
for  20,000  pistols,  contains  the  provision:  ".  .  .  the 
component  parts  of  pistols,  are  to  correspond  so  exactly 
that  any  limb  or  part  of  one  pistol,  may  be  fitted  to  any 
other  pistol  of  the  twenty-thousand."  But  a  later  contract 
for  carbines  (dated  May  2,  1839)  added  to  the  requirement 
for  uniformity  of  parts  and  interchangeability  the  provision 
that  this  must  be  done  "without  impairing  the  efficiency 
of  the  arms" — showing  already  an  evolution  in  preci- 
sion requirements  for  better  functioning  of  the  complete 
mechanism. 

This  early  contribution  to  the  economy  of  manufacture 
is  well  illustrated  by  Simeon  North's  biographers,  when  they 
quote  Daniel  Pidgeon's  reference1  to  the  Connecticut  man, 
whose  remarkable  blending  of  the  engineer  and  the  mechanic 
has  done  so  much  for  American  industry: 

His  method  of  attacking  manufacturing  problems  is  one  which, 
intelligently  handled,  must  command  markets  by  simultaneously 
improving  qualities  and  cheapening  prices. 

Continuous  Standardized  Production 

In  the  early  part  of  the  present  chapter,  interchangeable 
manufacture  was  referred  to  as  one  sort  of  repetition  manu- 

1  In  "Old  World  Questions  and  New  World  Answers,"  by  Daniel  Pidgeon. 


272  THE  CONTROL  OF  QUALITY 

facturing,  and  was  used  as  an  example  to  illustrate  the 
features  that  are  generally  applicable  in  repetition  work. 
In  explanation  of  the  statement,  attention  is  invited  to  the 
fact  that  interchangeable  work  applies  particularly  to  a 
mechanism  built  up  of  standardized  parts  in  such  a  way  as 
to  permit  disassembling  if  need  be.  For  even  pieces  that 
are  riveted  together  may  be  taken  apart.  On  the  other 
hand,  the  same  idea  of  standardized  work  applies  in  all 
kinds  of  manufacturing.  It  is,  in  fact,  at  the  root  of  suc- 
cess in  all  production,  and  for  precisely  similar  reasons. 

The  most  inclusive  definition  of  modern  manufacturing, 
from  this  aspect,  is  that  it  is  the  continuous  production  of 
articles  whose  qualities  have  been  standardized  within  given 
limits.  Since  errors  in  the  finished  product  mean  errors  all 
along  the  line  of  manufacture,  it  follows  as  a  corollary  to 
the  general  rule  that  the  unfinished  articles  should  be  simi- 
larly and  at  least  equally  standardized  at  each  stage  of  their 
manufacture. 

The  first  need  of  standardized  quality  arises  at  the  very 
beginning,  with  the  recovery  of  raw  materials  from  nature. 
Everything  in  nature  varies,  from  place  to  place  or  from 
season  to  season,  and  the  variations  are  large,  except  in 
unusual  cases.  It  makes  no  difference  whether  we  speak  of 
wheat,  cotton,  wool,  iron  ore,  lumber,  or  what-not.  It  is  the 
duty  of  the  basic  industries  which  prepare  these  materials 
so  that  they  are  suitable  for  use,  to  reduce  the  variations  as 
much  as  is  reasonably  possible. 

Resort  must  be  had  first  to  separation  of  the  raw  mate- 
rial into  classes  or  grades.  This,  in  a  sense,  divides  the  dif- 
ferences up,  and  thus  reduces  them  for  practical  purposes. 
As  a  second  step  in  the  ordinary  procedure,  two  courses  are 
open  and  usually  both  must  be  used.  Differences  due  to 
impurities  may  be  removed,  and  differences  in  size,  shape, 
and  so  on  rectified,  and  here  both  chemical  and  physical 


REPETITION  MANUFACTURING 


273 


processes  come  into  play.  Any  remaining  variations  from 
lot  to  lot  of  the  same  material  may  often  be  rectified  and  a 
larger  body  of  uniform  material  produced  by  using  the 
method  of  mixtures.  Finally  the  need  of  some  sort  of 
conditioning  process  may  be  indicated,  before  the  material 
is  ready  for  use  in  the  factory. 

Vital  Importance  of  Uniform  Quality  in  Raw  Materials 

The  importance,  in  repetition  manufacturing,  of  raw 
material  of  uniform  character  and  condition  cannot  be 
overstated.  Very  often_the  lack  of  such  uniformity  is  the 


IS 


Figure  62.     Set-Up  of  Johansson  Blocks  to  Check  Drill  Jig 


274  THE  CONTROL  OF  QUALITY 

root  source  of  the  subsequent  trouble  encountered  in  trying 
to  make  a  uniform  product.  What  is  the  value  of  accurately 
standardized  heat  treatment,  if  each  lot  of  steel  is  different  in 
behavior  from  its  predecessor?  It  is  cheaper  in  the  end  to 
start  with  material  of  uniform  character. 

It  may  seem  a  far  cry  from  steel  to  fibers  and  dyestuffs, 
but  the  principle  just  stated  holds  generally.  If  textiles  are 
manufactured  from  fibers  whose  affinity  for  dyes  varies  ma- 
terially from  lot  to  lot,  and  if  each  lot  of  dyestuff  is  of  dif- 
ferent hue  and  strength,  the  work  of  producing  articles 
uniform  as  to  color-matching  is  a  great  deal  more  difficult 
than  if  the  variations  are  reduced  or  removed  by  careful 
standardizing  of  the  raw  materials. 

One  often  hears  complaints  in  the  factory  about  lack  of 
uniformity  and  standard  quality  in  raw  materials,  but  what 
a  pitiful  admission  of  weakness  it  is  to  throw  the  blame  on 
the  producer  of  the  material.  He  can  hardly  be  expected 
to  know  the  needs  of  the  consumer,  and  if  the  man  who  uses 
the  material  will  make  his  exact  needs  known,  he  is  pretty 
apt  to  get  what  he  is  after.  Competition  will  gradually 
force  the  producer  of  material  into  line,  even  if  he  is  reluc- 
tant to  attempt  finer  standardization.  But  to  be  in  a  posi- 
tion to  call  for  better  materials,  the  manufacturer  must  first 
know  what  qualities  he  requires  and  why.  Also,  once  the 
required  standards  are  set,  means  must  be  provided  for 
measuring  the  incoming  deliveries,  for  it  is  useless  to  set 
standards  unless  one  is  prepared  to  enforce  them. 

The  factory  should  be  protected  by  filtering  out  unsuit- 
able material  at  the  receiving  platform  of  the  stockroom. 
This  is  the  first  place  for  the  application  of  control  labora- 
tories of  various  sorts:  physical,  chemical,  metallurgical,  or 
perhaps  some  new  kind  invented  for  the  needs  of  particular 
plants.  The  control  of  quality  begins  at  this  point,  in  so  far 
as  the  individual  factory  is  concerned. 


REPETITION  MANUFACTURING  275 

Continuous  Processing 

Perhaps  the  next  logical  class  of  industries,  after  the 
basic  order  of  raw  material  preparers,  is  that  large  group 
which  deals  with  the  assembling  of  various  raw  materials  by 
methods  which  involve  more  or  less  continuous  processing. 
Paper-making  and  textiles,  for  example,  are  highly  stand- 
ardized as  to  their  final  products,  which  must  be  suited  in 
each  case  to  meet  some  definite  need  of  the  consumer  and  to 
render  a  definite  service  in  relation  to  price. 

Now,  as  we  have  seen  already,  a  uniform  product  is  most 
economically  obtained  by  making  all  the  contributory  proc- 
esses equally  uniform,  as  nearly  as  may  be  with  consistency 
to  the  requirements  of  manufacturing  economy.  Weaving 
a  piece  of  cloth  on  the  loom  is  a  continuous  process  of  assem- 
bling various  standardized  elements  or  like  parts.  It  hardly 
can  be  called  interchangeable  work,  because  there  is  no 
possibility  of  interchanging  parts  after  the  goods  are  com- 
pleted. Yet  the  general  principle  of  standardization  of  the 
process  holds — it  is  advantageous  commercially  and  techni- 
cally to  hold  the  process  to  a  uniform  standard  within  speci- 
fied limits  or  allowed  variations. 

The  fact  that  the  errors  are  worked  into  the  goods  might 
seem  on  first  consideration  to  make  a  marked  difference 
between  this  type  of  manufacturing  and  so-called  inter- 
changeable work.  In  one  sense,  this  is  so,  but  from  the 
wider  viewpoint,  identical  principles  apply.  Thus  costs 
would  be  raised  to  prohibitive  levels  if  we  tried  to  eliminate 
all  broken  threads,  all  missing  picks,  and  all  other  defects — 
even  if  we  could  do  so.  The  only  practical  way  to  handle 
the  situation  is,  first,  to  define  what  kind  of  errors  and  what 
percentage  of  each  kind  are  to  be  allowed  for  a  given  stand- 
ard of  quality,  i.e.,  to  set  limits;  and  second,  gradually  to 
raise  these  standards  in  step  with  the  improvement  of  proc- 
esses, increase  in  workers'  skill,  and  so  on,  that  will  flow 


276 


THE  CONTROL  OF  QUALITY 


Figure  63.     Special  Milling  Fixture  Using  Johansson  Gage  Blocks  for  Locating 

Purposes 


REPETITION  MANUFACTURING  277 

from  attacking  the  production  problem  with  quality  as  our 
basic  criterion. 

Duplicate  Manufacturing 

There  is  a  large  class  of  manufacturing,  known  usually 
as  " duplicate  manufacturing,"  which  is  distinguished  by 
the  use  of  standards  (usually  of  size,  material,  and  form)  for 
the  product.  Screws,  nails,  and  many  other  kinds  of  hard- 
ware are  typical.  The  ordinary  uses  of  many  of  these 
articles  do  not  require  such  close  limits  as  the  manufacturer 
chooses  to  follow.  It  is  but  another  case  where  economy  of 
manufacture,  resulting  from  the  division  of  labor  and  the 
use  of  labor-saving  machinery,  dictates  the  adoption  of  the 
methods  of  standardized  repetition  work.  It  is  cheaper 
and  the  product  is  not  only  more  useful  but  in  every  way 
better,  because  quality  yields  to  control  when  processes 
are  standardized  and  quality  held  uniform — within  limits. 

Partial  Interchangeability 

In  the  case  of  assembled  mechanisms  the  various  classes 
of  repetition  work  differ  among  themselves,  chiefly  in  the 
degree  of  accuracy  with  which  the  component  parts  are 
made.  Thus,  in  passing  from  work  that  requires  fitting  to 
assemble,  we  find  a  sort  of  transitional  stage  before  we  reach 
the  ultimate  form  of  complete  interchangeability.  This  inter- 
mediate class  of  work  is  known  as  "selective  assembling." 
The  parts  are  accurate  enough  to  require  no  hand-work  to 
prepare  them  for  assembling,  but  are  not  sufficiently  stand- 
ardized to  permit  using  any  part  in  any  assembly.  Resort 
must  be  had  to  selecting  parts  that  go  together  properly. 

This  style  of  work  should  never  be  resorted  to  except 
when  the  processes  will  not  permit  of  the  precision  neces- 
sary for  complete  interchangeability,  which  sometimes  oc- 
curs; it  is  a  mistake  in  this  case,  just  as  it  is  generally  wrong 


278  THE  CONTROL  OF  QUALITY 

to  assume  that  loose  fits  make  for  easy  assembling,  except 
when  very  few  parts  are  mated.  A  long  series  of  inter- 
related parts  requires  close  work  if  the  assembling  is  to  be 
done  without  adjustment.  Such  considerations  at  once 
require  modification  of  the  generally  accepted  idea  that  low 
cost  and  easier  manufacture  are  best  obtained  through  al- 
lowing the  greatest  freedom  in  the  fit  of  mating  parts  with- 
out interfering  with  proper  functioning. 

The  advantages  of  true  interchangeability  may  be  ob- 
tained in  selective  assembling  if  the  selected  parts  are  first 
segregated  into  classified  sizes,  thus  simulating  inter- 
changeability  by  making  groups  of  parts  that  assemble 
without  selection. 

Production  of  Machine  Tools 

In  concluding  this  chapter  it  should  be  noted  for  com- 
pleteness, that  the  manufacture  of  machine  tools  follows  the 
general  rule,  but  occupies  a  middle  position.  Economy  of 
manufacture  requires  the  use  of  the  methods  of  interchange- 
able manufacture  in  the  tool-making  factory,  whenever  the 
quantity  made  warrants  its  adoption.  The  great  standard- 
ized markets  of  this  country,  by  providing  conditions  that 
permitted  the  use  of  such  methods,  are  largely  responsible 
for  our  advanced  position  in  machine  tool  development. 

The  fact  that  the  plants  which  are  the  users  of  the  ma- 
chine tool  maker's  product  must  standardize  their  proc- 
esses, makes  it  incumbent  on  the  tool  manufacturer  to 
provide  machines  that  are  highly  standardized  as  to  per- 
formance. But  machines  that  give  uniform  results  are 
best  made  uniform  in  all  their  parts,  and  so  the  chain  of 
uniformity,  once  started,  must  remain  unbroken.  It  may 
be  observed,  moreover,  that  the  quality  of  machine  tools 
should  be  controlled  to  a  greater  nicety  than  the  work  those 
machines  are  to  produce.  This  flows  from  the  fact  that 


REPETITION  MANUFACTURING  279 

there  is  an  unpreventable  slip  in  accuracy  between  the  work 
and  the  pattern  which  the  machine  follows  as  a  guide  in 
generating  the  work. 

This  need  for  great  precision,  combined  with  manu- 
facturing relatively  small  quantities  of  machines,  has  re- 
sulted in  a  certain  amount  of  hand-work  in  assembling. 
This  work  is  necessarily  done  by  highly  skilled  mechanics 
and  may  furnish  an  explanation  of  the  scattered  character 
of  the  inspection  organization  in  many  machine  tool  fac- 
tories. The  latter  situation  is  especially  interesting  at 
present  in  connection  with  the  overhauling  of  inspection 
methods  that  has  been  going  on  since  the  war  in  a  number  of 
these  factories. 

The  General  Principle 

We  have  just  traced  the  ideas  involved  in  the  continuous 
production  to  uniform  standards  of  quality.  Without  any 
attempt  toward  a  strict  classification  of  industries,  we  have 
analyzed  manufacturing  sufficiently  to  show  that  the  posi- 
tive and  continuous  control  of  quality  to  definite  standards 
within  limits  and  at  all  stages  of  manufacture  is  at  the  root 
of  production  economy.  Beginning  with  the  preparation  of 
raw  materials,  it  was  observed  that  the  same  principles  held 
good,  up  to  and  including  the  highest  type  of  interchange- 
able work.  In  the  latter  case  all  types  are  present.  Start- 
ing with  a  uniform  material  from  which  are  made  uniform 
parts,  these  like  finished  parts  in  their  turn  provide  a  uni- 
form raw  material  stock  for  the  assembler,  who  is  thus 
enabled  to  produce  uniform  articles  to  meet  some  special 
demand  of  the  ultimate  consumer.  The  latter  demands 
uniformity  because  his  needs  are  best  met  when  he  receives 
a  known  performance  and  a  known  return  in  quality  for  his 
money. 

At  each  stage  of  the  industrial  line  the  general  rule  ap- 


280  THE  CONTROL  OF  QUALITY 

plies — the  output  is  greater,  the  effort  is  less,  the  quality  is 
higher.  Hence  it  requires  less  of  the  consumer's  labor  to  ex- 
change for  a  higher  degree  of  satisfaction  of  his  needs;  and 
thus  the  economic  situation  of  everyone  is  improved. 

But  when  we  generalize  that  it  is  best  to  make  things 
uniform,  we  must  remember  always  that  quality  varies, 
and  that  what  we  really  mean  is  likeness,  uniformity,  or 
standardization  of  quality  within  limits.  This,  in  a  word, 
is  why  quality  requires  control. 


CHAPTER  XVII 
THE  DIMENSIONAL  CONTROL  LABORATORY 

Practical  Value  of  Precision 

The  most  important  advantages  of  precise  dimensional 
accuracy  in  manufacturing  the  component  parts  of  an  as- 
sembled mechanism  are: 

1.  The  elimination  of  hand-fitting,  with  quicker  and 

cheaper  assembling. 

2.  More  even  wear  with  consequent  greater  resistance 

to  wear  and  longer  life  in  service,  with  correct 
functioning  of  parts. 

3.  Less  noise  after  use,   smoothness  of  action,  and 

smaller  power  losses.  "Noise  is  an  automatic 
alarm  indicating  lost  motion  and  wasted  energy. 
Silence  is  economy.  .  .  .MI 

With  the  possible  exception  of  some  of  the  makers  of 
very  high-grade  machine  tools,  probably  no  industry  has 
advanced  precision  workmanship  to  such  a  high  degree  of 
perfection  as  the  automotive  manufacturers.  It  is  in  recog- 
nition of  this  fact,  and  with  admiration  for  their  achieve- 
ments, that  we  must  turn  to  them  for  examples  of  what  our 
methods  should  be  in  seeking  to  bring  dimensional  quality 
under  control.  For  this  reason  much  of  the  accompanying 
illustrative  matter  is  taken  from  automobile  factories.  The 
lessons  are  by  no  means  confined  in  application  to  that  in- 
dustry. 

The  basic  requirement  of  precision  is  that  means  shall 
be  provided  for  making  very  exact  measurements,  and  the 

1  From  "Creative  Chemistry,"  by  Edwin  E.  Slosson. 

28l 


282 


THE  CONTROL  OF  QUALITY 


THE  DIMENSIONAL  CONTROL  LABORATORY     283 

most  sensible  way  to  secure  proper  surroundings  for  the  use 
of  this  equipment  is  to  provide  a  central  place  suitably  de- 
signed for  this  purpose. 

The  Laboratory  Proper 

Since  uniformity  of  conditions  is  the  great  essential  of 
manufacturing,  it  is  even  more  necessary  for  a  control  center 
of  quality  in  manufacturing.  Let  us  now  consider  some  of 
the  things  which  require  attention  at  such  a  control  point,  in 
order  that  influences  which  are  disturbing  to  the  personnel  or 
destructive  to  the  equipment  may  be  reduced  to  a  minimum. 

Temperature  changes,  the  greatest  cause  of  variation,  due 
to  weather  changes,  can  be  eliminated  by  providing  artifi- 
cial heat  and  cold,  under  uniform  control.  When  this  is 
done  the  temperature  is  held  around  70°  F.  There  remain 
then  three  other  principal  causes  of  disturbance :  body  heat 
of  operators,  heat  differences  of  objects  brought  in  from  out- 
side, and  heat  from  light  rays.  The  first  can  be  dealt  with 
in  various  ways  which  are  obvious,  such  as  specially  insulat- 
ed holding  places  on  instruments.  (See  Figure  52,  page  222.) 
Anything  brought  in  from  outside  should  be  allowed  to 
stand  until  temperature  equilibrium  has  been  reached. 
When  heat  from  rays  of  sunlight  or  from  an  electric  light 
near  the  work  is  permitted  to  affect  either  work  or  instru- 
ments, a  serious  error  is  likely  to  occur.  For  small  dimen- 
sions, direct  expansion  is  quite  small  (for  tempered  steel  it 
is  about  0.0007  mcn  per  inch  for  one  hundred  Fahrenheit 
degrees,  nevertheless  the  effect  may  be  specially  serious 
when  direct  expansion  is  magnified  by  lever  action,  e.g.,  sun- 
light striking  the  anvils  of  a  snap  gage  for  a  few  minutes 
would  have  little  effect,  but  might  easily  be  serious  if  allowed 
to  shine  on  the  handle  side,  because  the  effect  of  the  direct 
expansion  would  be  increased  and  thereby  materially  change 
the  distance  between  the  anvils. 


284  THE  CONTROL  OF  QUALITY 

Humidity  and  cleanliness  are  matters  requiring  consid- 
eration. It  would  not  be  extremely  difficult  or  costly  to 
make  the  measuring  room  dustproof  and  to  supply  washed 
dry  air  in  connection  with  temperature  control.  The  many 
advantages  hardly  require  mention.  Such  a  system  would 
seem  especially  desirable  in  moist  climates,  where  polished 
steel  rusts  almost  overnight  at  certain  seasons  of  the  year. 
Any  system  of  the  sort  should  have  automatic  control  and 
should  be  designed  to  run  continuously,  as  it  will  not  make 
for  uniformity  if  operated  only  during  working  hours. 

As  regards  lighting,  daylight  illumination  should  be  from 
the  north  in  order  to  avoid  the  admission  of  direct  sunlight. 
Greater  uniformity  and,  with  certain  work,  better  definition 
will  be  secured  for  local  illumination  if  the  artificial  light  is 
taken  from  ''artificial  daylight"  lamps  instead  of  ordinary 
tungstens.  The  Trutint  lamps  made  by  the  Nela  Special- 
ties Division  of  the  National  Lamp  Works  (General  Electric 
Company)  are  made  in  an  inexpensive  factory-type  fixture 
suitable  for  such  work.  Care  should  be  taken  to  place 
artificial  lights  for  local  illumination  so  that  their  heat  will 
not  be  concentrated  in  objectionable  ways.  Good  general 
illumination  requires  white  or  light  neutral  gray  walls,  with 
a  dark  dado  at  the  bottom.  It  is  always  bad  to  have  light 
shining  from  below  the  bench  level. 

Vibration  and  noise  should  be  avoided  as  much  as  is  con- 
sistent with  convenient  location  of  the  room ;  the  latter  be- 
cause it  is  a  distraction,  the  former  because  it  is  likely  to 
interfere  with  close  reading.  Accurate  work  with  optical 
projection  apparatus  which  makes  use  of  the  optical  lever 
for  magnifying  (for  screw  threads,  shape,  etc.),  is  out  of  the 
question  if  vibration  is  present  to  any  appreciable  extent, 
and  for  such  work  a  separate  room  may  be  required,  well 
removed  from  the  machine  shops. 

Floor  covering  may  be  wood,  or,  better  still,  battleship 


THE  DIMENSIONAL  CONTROL  LABORATORY     285 

linoleum,  which  may  reduce,  if  not  avoid,  the  occasional 
accidental  error  due  to  dropping  things. 

Furnishings  should  be  limited  to  articles  of  use  in  the 
work,  but  all  furnishings  should  be  first  class  and  kept  so. 
The  laboratory  is  no  place  for  an  old  wooden  work  bench  or 
rickety  stools.  There  should  be  shelf  space  in  cabinets  for 
all  equipment  not  in  use,  and  safe  cabinets,  or  preferably 
vaults,  for  master  control  standards  and  models.  A  con- 
venient wash  basin  should  be  provided,  unless  there  is  a 
complete  toilet  room  handy.  In  the  checking  of  accurate 
measurements  the  tactile  sense  is  no  more  helped  by  a  coat 
of  grease  and  dirt  than  it  is  in  mechanical  drawing. 

The  Surface  Plate 

A  true  plane  surface  supplies  the  level  foundation  upon 
which  we  build  for  accuracy.  The  control  laboratory  should 
have  one  large  surface  plate  say,  4  or  5  feet  by  8  feet, 
mounted  on  a  firm  foundation.  Such  a  plate  is  of  massive 
construction  and  is  not  likely  to  become  distorted  from 
irregularities  of  the  supporting  structure;  nevertheless  it  is 
certain  to  change  with  age  and  use,  even  if  it  is  made  from 
well-aged  metal  in' the  first  place.  Consequently,  it  should 
be  watched  very  carefully,  and  this  may  develop  the  need 
for  resurfacing  at  least  once  in  its  career.  The  danger  of 
its  being  affected  by  temperature  changes  is  slight,  if  the 
laboratory  is  kept  at  nearly  standard  temperature. 

With  careful  surfacing  when  needed,  it  should  be  possible 
to  keep  the  surface  within  o.ooi  inch  of  a  true  plane  for  the 
greater  portion  of  its  area ;  yet  every  surface  plate  will  have 
small  hills  and  valleys  whose  location  should  be  known  and 
allowed  for  in  placing  work  for  measuring.  Large  accurate 
measurements  should  be  checked  by  placing  the  work  in 
different  positions.  In  checking  the  plate  to  locate  these 
irregularities,  the  first  step  should  be  to  apply  a  long  and 


286  THE  CONTROL  OF  QUALITY 

accurate  straight  edge  (with  reinforced  ribbed  back)  and  use 
a  feeler  gage.  The  second  step  should  be  to  sweep  the  plate 
thoroughly  with  a  surface  gage,  mounting  a  sensitive  dial 
indicator  at  the  end  of  the  arm,  a  short  arm  being  first  used 
and  then  a  long  extended  arm.  If  a  further  check  is  desired , 
recourse  may  be  had  to  the  method  Whitworth  used  in 
creating  the  first  standard,  namely,  by  contact  application 
of  other  plates,  using  Prussian  blue  between  the  plates  to 
show  the  humps  and  hollows  revealed  by  rubbing  them  to- 
gether. In  ordinary  shop  practice  a  smaller  surface  plate 
may  be  used  for  this  purpose. 

Where  much  work  is  to  be  done,  and  for  other  reasons  of 
convenience,  it  is  desirable  to  have  one  or  more  smaller  sur- 
face and  bench  plates.  It  is  idle,  however,  to  attempt  small 
measurements  accurate  to  ten  thousandths  with  such  equip- 
ment. For  such  work  optically  correct  plates  should  be 
used.  The  crome  alloy  steel,  tool-makers'  flats  manufac- 
tured by  the  Pratt  and  Whitney  Company,  are  about  5 
inches  in  diameter  by  %  inch  thick,  hardened  and  heat 
treated  by  a  special  stabilizing  process.  They  are  finished 
by  the  Hoke  method  of  lapping  (like  the  Pratt  and  Whitney 
Hoke  precision  gages)  with  surfaces  (top  and  bottom)  fin- 
ished flat,  well  within  .000,01  inch  and  parallel  within  half 
that  error.  Precision  gages  will  wring  onto  them  as  they 
wring  onto  each  other. 

The  Dimensional  "Court  of  Highest  Appeal" 

Prior  to  the  invention  of  the  Swedish  gage  blocks,  the 
measuring  machine  was  the  only  available  device  for  very 
accurate  measurements.  For  some  kinds  of  measuring, 
such  as  occur  in  originating  or  duplicating  manufacturing 
standards,  an  instrument  of  this  type  is  highly  important. 
Some  sort  of  end  measure  (rod  or  bar)  is  often  needed  to 
check  positively  an  accurate  large  dimension,  and  it  would 


THE  DIMENSIONAL  CONTROL  LABORATORY  287 

be  difficult  to  conceive  of  an  easier  way  of  insuring  accuracy 
than  by  the  use  of  a  measuring  machine. 

Resort  to  such  instruments  was  necessitated  by  the 
early  attempts  to  obtain  real  standards  of  length.  In  1742 
beam  compasses  were  used  for  that  purpose  in  England, 
using  both  parallel  jaws  and  pointed  ends  as  usual.  By  the 
use  of  micrometer  screws  with  graduated  heads  this  instru- 
ment was  considered  accurate  to  within  0.000,62  inch  for 
comparing  yard  length  standards.  At  the  same  time  the 
French  compared  their  standards  to  0.003  inch,  until  La 
Condamine,  in  1758,  said  they  should  be  compared  to  o.ooo,- 
89  inch,  "if  our  senses  aided  by  the  most  perfect  instruments 
can  attain  to  that."  Fifty  years  later  a  lever  comparator 
was  designed  by  Lenoir,  "which  was  regarded  as  trust- 
worthy to  0.000,077  inch."  The  use  of  high-powered  micro- 
scopes in  combination  with  a  carefully  graduated  scale  in 
later  measuring  instruments  has  brought  this  error  down  to 
0.000,01  inch,  although  accurate  comparison  of  length 
standards  of  3  feet  and  greater  encounter  a  number  of  com- 
plications, principally  due  to  molecular  forces  in  the  ma- 
terial and  to  temperature  effects.2 

From  these  beginnings  various  types  of  measuring 
machines  have  been  evolved.  There  are  several  European 
models  of  modern  design,  while  in  this  country  the  Brown 
and  Sharpe  measuring  machine  (see  Figure  65)  and  the 
Pratt  and  Whitney  machine  (see  Figure  66)  are  well  known. 

The  Brown  and  Sharpe  Measuring  Machine 3 

The  Brown  and  Sharpe  measuring  machine  (shown  in 
Figure  65)  operates  on  the  principle  of  taking  measurements 
by  means  of  a  moving  scale  under  a  microscope,  used  in 

2  See  Harkness,  "  The  Progress  of  Science  as  Exemplified  in  the  Art  of  Weighing  and  Measur- 
ing," for  these  and  further  details.     The  way  in  which  these  figures  are  stated  is  significant  of 
the  earlier  failure  to  appreciate  the  principles  of  the  precision  of  measurement. 

3  From  data  supplied  through  the  courtesy  of  Luther  D.  Burlingame,  Industrial  Superin- 
tendent of  the  Brown  and  Sharpe  Manufacturing  Company,  Providence,  R.  I. 


288 


THE  CONTROL  OF  QUALITY 


THE  DIMENSIONAL  CONTROL  LABORATORY  289 

conjunction  with  a  micrometer  screw  and  vernier,  the  entire 
mechanism  being  supported  upon  a  rigid  bed  of  accurately 
careful  construction.  Measurements  are  taken  directly 
from  the  scale  and  the  machine  can  be  set  to  measure  up  to 
1 6  inches. 

The  micrometer  wheel  is  graduated  to  read  to  o.oooi 
inch  and  the  vernier  plate  used  in  connection  with  the  wheel 
makes  it  possible  to  read  to  0.000,01  inch.  The  accuracy 
of  the  machine,  of  course,  rests  fundamentally  upon  direct 
readings  taken  from  the  graduations  of  the  scale,  and  thus 
depends  upon  the  perfection  of  the  scale  and  the  micrometer 
screw.  The  sensitivity  of  the  machine  may  be  shown  by 
placing  the  hand  on  the  bed  plate  between  the  slides  and 
holding  it  there  for  approximately  60  seconds,  at  the  end  of 
which  time  the  piece  will  drop  from  between  the  measuring 
points.  It  is  interesting  to  note,  however,  that  the  ma- 
chine requires  about  20  minutes  to  return  to  its  normal 
condition  after  this  test. 

The  Pratt  and  Whitney  Standard  Measuring  Machine 4 

The  well-known  measuring  machine  made  by  the  Pratt 
and  Whitney  Company  of  Hartford,  Connecticut  (shown  in 
Figures  66  and  67)  provides  not  only  a  scientific  instrument 
for  use  in  the  laboratory,  but,  because  of  simplified  and 
standardized  methods  of  manufacture,  it  is  sold  at  a  price 
which  permits  its  wide  commercial  use  and  allows  any  man- 
ufacturer to  originate  or  duplicate  his  own  standards. 

The  four  principal  factors  which  determine  the  ac- 
curacy of  this  machine  are  the  bed,  the  dividing  screw,  the 
control  of  the  measuring  pressure,  and  the  standard  bar 
from  which  the  sliding  head  is  located  in  known  relation- 
ship to  the  stationary  head. 

The  bed  is  of  cast  iron,  seasoned,  machined,  and  lapped 

4  From  information  furnished  through  the  courtesy  of  Oscar  E.  Perrigo,  M.  E.,  engineering 
department,  Pratt  and  Whitney  Company. 

19 


290 


THE  CONTROL  OF  QUALITY 


straight  and  parallel  for  its  entire  length,  and  the  processes 
through  which  it  passes  are  of  such  a  nature  that  the  finished 
product  is  not  materially  affected  by  changes  of  tempera- 


Figure  66.     Pratt  and  Whitney  Measuring  Machine 

ture  or  torsional  strains  which  would  tend  to  destroy  its 
accuracy. 

f  The  dividing  screw  for  the  sliding  head  is  cut  on  a  spe- 
cially designed  engine  lathe  which  is  kept  in  the  laboratory 
where  a  uniform  temperature  is  maintained  at  all  times. 


THE  DIMENSIONAL  CONTROL  LABORATORY  291 

Compensating  devices  and  adjustment  provide  a  screw  of  a 
degree  of  accuracy  far  beyond  that  hitherto  produced. 

The  mechanism  for  controlling  the  measuring  pressure 
is  located  in  the  stationary  head.  The  control  is  accom- 
plished by  means  of  a  sensitive  spring  arranged  so  that  when 
pressure  is  applied  to  the  measuring  anvil  it  is  communicated 
to  another  pair  of  anvils  between  which  a  small  plug  is  sus- 
pended by  spring  tension.  When  the  exact  measuring  point 
is  reached  the  little  plug  drops  from  a  horizontal  to  a  vertical 
position  indicating  that  the  reading  can  be  taken.  By  this 
means  the  human  element  is  eliminated,  with  the  result 
that  accurate  measurements  can  be  duplicated  indefinitely 
without  dependence  upon  the  "feel"  of  the  operator. 

The  fourth  factor  is  the  method  of  locating  the  sliding 
head  in  a  known  relationship  to  the  stationary  head.  This 
is  accomplished  by  means  of  a  standard  bar  located  at  the 
rear  of  the  machine.  Mounted  on  this  bar  are  a  series  of 
buttons  with  highly  polished  faces  upon  which  are  etched 
fine  lines  exactly  I  inch  (or  25  millimeters)  apart.  The 
graduations  on  the  standard  bar  are  transferred  by  specially 
designed  apparatus  from  a  known  bar  furnished  by  the 
Bureau  of  Standards  at  Washington,  D.  C.,  which,  needless 
to  say,  is  accurate  to  within  the  narrowest  limits  permitted 
by  human  skill. 

In  taking  measurements  the  index  circle  is  set  to  zero  and 
the  sliding  head  located  to  the  zero  line  on  the  standard  bar. 
A  microscope  (C,  Figure  67)  equipped  with  an  electric  light 
enables  the  etched  line  to  be  seen,  the  microscope  tube  being 
adjustable  so  as  to  obtain  a  clear  definition.  When  the 
cross  line  drawn  on  the  ground  glass  at  the  bottom  of  the 
microscope  coincides  exactly  with  the  etched  line  at  zero  on 
the  standard  bar  K,  the  tailstock  (A ,  Figure  66)  is  moved  up 
into  contact  (indicated  by  the  fall  of  the  drop  plug)  and 
locked  in  position,  where  it  remains. 


292 


THE  CONTROL  OF  QUALITY 


After  the  stationary  head  is  located,  the  sliding  head  is 
moved  back,  and  then  relocated,  the  compensating  zero  ad- 
justment F  taking  care  of  any  variation  of  position.  A 
tangent  screw  G  and  lock  screw  H  are  provided  on  the  index 
circle  for  obtaining  the  last  fine  adjustment  when  taking 
measurements.  Its  multiplied  leverage  provides  a  slow 


6  * 


Figure  67.    Details  of  Measuring  Head — Pratt  and  Whitney  Measuring  Machine 


THE  DIMENSIONAL  CONTROL  LABORATORY      293 

easy  movement  of  the  dividing  screw  and  prevents  "going 
by  "  the  measuring  point  (when  the  drop  plug  falls  clear  out 
of  contact).  The  index  circle  is  also  provided  with  a  mag- 
nifying glass  E  for  easier  reading  of  the  scale,  which  is  gradu- 
ated to  I/ 10,000  inch  (or  1/500  millimeter).  There  are  400 
divisions  on  the  English  circle  and  500  on  the  metric.  One 
turn  of  the  circle  is  indicated  on  the  linear  scale  L. 

Vernier.  The  index  circle  divisions  (.0001  inch,  or  1/500 
millimeter)  can  be  subdivided  five  times  by  estimation  on 
the  older  machines,  but  to  assist  in  obtaining  very  fine  ac- 
curate measurements,  a  vernier  is  now  supplied  which  will 
subdivide  to  .000,01  of  an  inch,  or  1/5,000  millimeter. 
Adjustments  are  provided  to  take  up  any  wear  in  the  divid- 
ing screw  should  it  ever  occur.  All  anvils  are  hardened, 
ground,  and  lapped  flat  and  parallel,  and  with  reasonable 
care  the  entire  machine  will  give  accurate  service  for  years 
with  the  simplest  of  adjustments. 

The  machines  are  set  and  are  standard  at  62°  F.  It  is 
not  necessary  to  use  them  at  the  initial  temperature,  as 
variations  will  affect  both  the  work  and  machine  practically 
alike.  When  used  for  scientific  research,  however,  the  ini- 
tial temperature  should  be  closely  adhered  to.  '  The  ma- 
chines are  regularly  furnished  in  12,  24,  36,  48,  and  80 
inch,  or  300,  600,  1,000,  1,200,  and  2,000  millimeter  measur- 
ing lengths. 

Cylindrical  supports  (B)  for  holding  work  to  prevent 
springing,  are  furnished  regularly  with  the  machines  as 
follows: 

Two  with  12-inch  or    300  millimeter 
Three   "     24    '  600 

Four  36    '        "  1,000 

Four  48  "  1,200 

Six  80    '        "2,000 

The  machine  regularly  requires  no  special  foundation,  as 
it  has  a  three-point  bearing  on  the  case  for  equalization. 


294  THE  CONTROL  OF  QUALITY 

The  Johansson  or  Swedish  Block  Gages 

We  now  open  one  of  the  most  interesting  pages  of 
modern  technical  achievement — a  story  of  little  blocks  of 
steel  of  unbelievable  fineness  of  workmanship.  It  was  in- 
deed fortunate  for  the  development  of  greater  precision 
in  machine  shop  processes  that  a  man  of  the  mental  qual- 
ities of  C.  E.  Johansson  happened  to  work  in  a  govern- 
ment arsenal  engaged  in  the  manufacture  of  military  small 
arms. 

The  technique  of  this  business  several  years  ago  required 
something  more  nearly  absolute  in  accuracy  than  the 
measuring  methods  generally  in  use  at  that  time  in  machine 
shop  work,  for  it  was  highly  desirable  to  make  military  fire- 
arms with  the  greatest  degree  of  precision  that  was  reason- 
ably obtainable.  In  order  to  insure  this  result,  I  believe  I 
am  correct  in  stating,  it  was  the  usual  practice  to  resort  to 
positive  end  measures  for  all  important  dimensions,  these 
measures  being  used  for  checking  master  or  reference  gages. 
The  consequence  was  that  each  government  arsenal  soon 
accumulated  a  large  quantity  of  such  gage  templates,  or  end 
measures,  which  constituted  their  own  dimensional  stand- 
ards. This  will  account  for  the  fact  that  by  the  use  of 
modern  finely  standardized  measurements  certain  govern- 
ment arsenals  have  been  found  to  be  using  an  inch  which 
varies  slightly  from  the  standard  inch.  It  is  interesting  also 
to  note  in  passing  that  the  use  of  limit  gages  is  of  fairly  recent 
adoption  for  such  work.  The  output  was  generally  small 
(being  just  enough  to  keep  the  arsenal  busy  in  peace  time), 
so  that  an  organization  of  very  highly  skilled  men  was  de- 
veloped. Owing  to  their  finely  cultivated  sensitiveness  of 
touch,  and  by  taking  careful  precautions  in  gage-checking, 
these  men  were  able  to  produce  extremely  accurate  work, 
using  a  single  fixed  dimension  on  the  working  gage.  All  of 
this  procedure  resulted  in  the  accumulation  of  a  very  large 


THE  DIMENSIONAL  CONTROL  LABORATORY  295 

quantity  of  end  measures  whose  exact  values  in  terms  of  the 
standard  inch  were  not  known  with  any  special  precision. 

C.  E.  Johansson,  after  three  years  in  the  United  States, 
during  which  he  acquired  both  a  practical  and  a  theoretical 
education,  returned  to  Sweden  and  shortly  afterward  began 
his  work  as  a  tool-maker  in  the  Carl  Gustavs  Stads  arms 
factory  at  Eskilstuna,  Sweden ;  later  he  became  tool-room 
foreman.  He  soon  came  to  note  that  the  usual  measuring 
equipment  differed  in  its  results,  which  lead  him  to  attempt 
the  creation  of  a  system  of  measuring  for  such  work  which 
would  give  beyond  question  the  accuracy  required.  Realiz- 
ing the  great  value  of  solid  blocks  of  steel,  or  end  measures, 
and  guided  by  the  experience  gained  in  the  arsenal  (which 
adopted  the  tolerance  or  limit  system  in  1889,  so  that  parts 
could  be  made  in  quantities  and  assembled  without  fitting) 
he  proceeded  to  develop  the  famous  Swedish  or  Johansson 
block  gages,  which  in  1906  he  announced  to  the  mechanical 
industries  at  large. 

Much  more  recently  a  factory  has  been  established  at 
Poughkeepsie,  New  York,  for  the  manufacture  of  the 
Johansson  standards  in  this  country,  where  they  find  a 
wide  application  in  industry. 

These  blocks  possess  the  following  interesting  character- 
istics : 

1.  They  are  made  of  steel  which  has  been  heat  treated 
and  seasoned  to  practically  eliminate  warping  or  "growing." 

2.  The  surfaces  are  flat  and  parallel  to  within  .000,01 
inch  or  less. 

3.  These  parallel  surfaces  are  distant  from  each  other  to 
within  .000,01  inch  or  less  of  the  absolute  dimensions  stated 
on  the  block. 

4.  These  accurate  surfaces  permit  of  wringing  the  blocks 
together,  and  they  are  arranged  as  to  dimension  so  that  by 
suitable  combinations  of  the  blocks,  as  indicated  in  the  va- 


296  THE  CONTROL  OF  QUALITY 

rious  illustrations,  practically  any  dimension  desired  may 
be  obtained  without  appreciable  error. 

When  packed  together  in  this  manner,  not  only  is  the 
variation  per  inch  kept  as  low  as  .000,01  inch  or  less,  but  the 
surfaces  are  in  such  perfect  contact  that  they  adhere  to  each 
other  (probably  because  of  surface  tension  of  the  minute 
film  of  oil  between  them)  with  a  force  far  in  excess  of  mere 
atmospheric  pressure.  It  is  almost  certain  to  result  in 
"freezing,"  if  the  blocks  are  left  in  contact  for  several  hours. 

As  will  be  observed  from  the  various  illustrations,  posi- 
tive end  measures  of  this  sort  find  wide  and  useful  applica- 
tion in  any  tool  work  that  requires  accurate  determination 
of  dimension.  No  matter  how  many  sets  are  used  in  the 
factory — and  it  is  an  economy  to  use  several — each  dimen- 
sional control  laboratory  should  be  equipped  with  one  set  of 
such  blocks  to  be  retained  solely  as  a  final  check  for  dimen- 
sional control  purposes.  If  the  blocks  are  given  proper  care, 
they  should  remain  practically  unchanged  from  year  to  year. 
Ordinary  inaccuracies  due  to  wear,  accident,  or  abuse,  may 
be  discovered  quite  readily  by  checking  them  against  each 
other  in  different  combinations.  The  result  is  a  court  of 
last  appeal  for  dimension  in  the  fool-proof  form  of  flat  steel 
blocks,  or  end  measures,  in  fixed  sizes. 

As  an  example  of  continued  precision  of  the  block,  it  may 
be  noted  that  a  set  (No.  3353)  purchased  in  October,  1918, 
was  returned  to  the  Johansson  Company  in  October  of  1920 
for  rechecking.  This  set  bore  an  engraved  copper  plate  on 
the  box  stating  that  it  was  to  be  used  only  for  checking  other 
Johansson  standard  blocks  and  could  be  used  only  upon 
requisition  by  certain  specified  officials  of  the  owning  com- 
pany, which  happened  to  be  the  Ford  Motor  Company. 
This  reference  set,  of  course,  had  received  excellent  attention 
and  very  slight  use.  Inspection  by  the  Johansson  Company 
at  Poughkeepsie  showed  that  two  blocks  had  worn  approxi- 


THE  DIMENSIONAL  CONTROL  LABORATORY      297 

mately  .000,01  inch  below  normal  size.  All  the  rest  of  the 
blocks,  including  the  2,  3,  and  4  inch  blocks,  showed  varia- 
tions from  normal  size  of  less  than  .000,01  inch  and  most  of 
them  less  than  .000,005  inch.5 

The  Johansson  methods  of  manufacture  and  measure- 
ment have  been  kept  a  business  secret,  although  Mr.  Johans- 


Figure  68.     Special  Set  of  Johansson  Block  Gages 
Accurate  to  within  one-millionth  of  an  inch. 

son  has  disclaimed  the  use  of  the  interferometer  or  light 
wave  method  of  measuring,  which  has  caused  a  good  deal  of 
speculation  on  the  part  of  mechanical  engineers  and  tool- 
makers  as  to  just  what  method  of  measurement  he  uses. 
Despite  the  absence  of  information  on  this  subject,  we 
must  nevertheless  admire  so  remarkable  an  achievement. 
In  fact,  one  can  form  a  fairly  good  idea  of  how  much 
mechanical  sense  anyone  has  by  observing  his  attitude 

5  From  information  furnished  by  Huber  B.  Lewis,  Vice-President,  C.  E.  Johansson,  Inc., 
Poughkeepsie,  N.  Y. 


298  THE  CONTROL  OF  QUALITY 

toward  the  Swedish  block  gage  itself.  As  an  example  of 
what  can  be  done,  attention  is  invited  to  the  set  shown  in 
Figure  68,  which  was  made  by  Mr.  Johansson  in  order  to 
provide  a  set  of  blocks  accurate  within  the  one-millionth 
part  of  an  inch. 

The  Pratt  and  Whitney  Precision  Gages 

During  the  war  the  need  for  precision  end  measures  of 
the  Swedish  type  was  greatly  increased,  and  it  is  much  to  the 
credit  of  the  United  States  Bureau  of  Standards  that  it 
became  possible  to  develop  very  precise  gage  blocks  through 
the  Hoke  method  of  lapping  and  the  use  of  the  interference 
of  light  waves  for  measuring.  William  E.  Hoke  of  St.  Louis 
began  this  development  with  the  Bureau  of  Standards,  and 
later  as  a  major  in  the  Ordnance  Department  was  enabled 
to  make  further  progress.  Gage  blocks  are  now  made  by 
several  concerns  in  the  United  States.  An  interesting  de- 
scription of  how  the  Hoke  type  of  gages  are  made  by  the 
Pratt  and  Whitney  Company  may  be  found  in  the  April, 
1920,  issue  of  Machinery.  The  method  of  measuring  by  the 
utilization  of  light  waves  is  described  in  the  May  22,  1919, 
issue  of  the  Iron  Age. 

Comparators 

It  will  be  noted  from  a  number  of  the  illustrations  of 
gage  blocks  in  use  that  the  blocks  are  being  applied  with  the 
assistance  of  an  instrument  for  accurately  comparing  meas- 
urements. Figure  69,  for  example,  shows  the  blocks  being 
used  with  an  American  amplifying  gage,  as  made  by  the 
American  Gage  Company  of  Dayton,  Ohio.  The  American 
amplifier  operates  on  the  lever  principle  re-enforced  by  a 
dial  indicator,  as  shown  in  the  illustration.  Figure  38 
shows  a  similar  application,  using  the  Prestometer  or  Prest- 
wich  fluid  gage,  as  supplied  by  the  Coats  Machine  Tool  Com- 


THE  DIMENSIONAL  CONTROL  LABORATORY     299 


Figure  69.     American  Amplifying  Gage  Used  with  Swedish  Gage  Blocks 


300  THE  CONTROL  OF  QUALITY 

pany,  Inc.,  of  New  York.  The  Prestwich  fluid  gage  largely 
eliminates  the  sense  of  touch  and  measures  differences  of 
dimension  with  extreme  accuracy  through  the  use  of  fluids 
and  capillary  tubes  in  connection  with  metal  diaphragms 
and  a  micrometer  scale.  If  this  instrument  is  used  with 
care  in  the  selection  of  suitable  sized  tubes  for  the  work  in 
hand,  and  if  the  adjustments  are  made  with  reasonable  atten- 
tion to  the  elimination  of  air  bubbles,  setting  to  zero,  etc., 
it  is  an  invaluable  auxiliary  device  for  use  with  gage  blocks. 
While  it  is  true  that  fairly  accurate  comparisons  may 
be  made  by  using  the  holders  or  straight  edges  provided 
with  the  gage  block  sets,  very  precise  comparisons  are  much 
simplified  by  using  an  instrument  of  the  comparator  type, 
in  which  differences  in  reading  are  magnified  by  some  form 
of  mechanical  or  fluid  lever  and  the  reading  scales  of  which 
can  be  set  to  zero  for  each  dimension. 

Miscellaneous  Equipment 

Various  well-known  miscellaneous  auxiliary  equipment 
for  measuring  are  listed  in  detail  in  most  small  tool  cata- 
logues, and  these  should  be  found  in  every  dimensional 
control  laboratory.  New  devices  of  considerable  usefulness 
are  continually  coming  to  the  front,  however,  such  as  the 
following : 

1.  Optical  projection  apparatus  for  comparing  screw 
threads  and  profiles  is  valuable  for  several  purposes,  as  re- 
ferred to  in  ChapterXIXon  the  gaging  of  screw  threads.     It 
should  be  noted  that  such  apparatus  requires  freedom  from 
vibration. 

2.  The  Johansson  set  of  precision  angle  blocks.    Thisisa 
very  useful  outfit  for  precisely  checking  angles  and  should 
find  much  wider  application. 

3.  While  not  directly  connected  with  dimension,  various 
control  instruments  for  measuring  hardness,  such  as  the 


THE  DIMENSIONAL  CONTROL  LABORATORY  301 

Brinell  tester  and  the  Shore  scleroscope,  should  form  part  of 
the  laboratory  equipment.  The  Bureau  of  Standards 
Technologic  Paper  No.  1 1  gives  a  "  comparison  of  five  meth- 
ods used  to  measure  hardness." 

Personnel 

Thus  far  only  the  material  equipment  of  an  ideal  dimen- 
sional control  center  has  been  discussed.  Needless  to  say, 
the  selection  of  the  personnel  of  such  a  control  center  is  also 
extremely  important.  Probably  everyone  inexperienced  in 
the  use  of  measuring  apparatus  starts  out  with  the  idea  that 
manual  dexterity  and  tactile  sense  is  associated  only  with 
the  slender  tapering  fingers  of  the  so-called  artistic  hand. 
But  any  such  notion  is  quickly  dispelled  by  observing  the 
accurate  work  turned  out  by  men  with  fat  pudgy  fingers. 
The  only  proper  and  scientific  test  of  measuring  ability  is 
actual  trial.  There  is  no  reason  why  candidates  for  jobs  of 
this  kind  should  not  be  tried  out  by  actual  measurement  of 
their  work,  which  will  soon  reveal,  if  the  test  is  scientifically 
conducted,  any  lack  of  tactile  sense,  accurate  eyesight,  or 
skilfulness  in  making  fine  adjustments. 

One  of  the  first  requisites  for  the  proper  use  of  scientific 
apparatus  is  cleanliness.  The  laboratory  itself  should  be 
kept  immaculately  clean  and  clear  of  everything  except  what 
is  needed  for  the  work  in  hand.  The  same  comment  applies 
to  the  personnel,  who  should  be  encouraged,  by  the  provi- 
sion of  facilities  for  washing,  to  keep  their  hands  clean.  In 
hot  weather  this  may  be  especially  important,  because 
there  are  some  people  whose  perspiration  quickly  rusts  and 
soon  destroys  highly  polished  steel  surfaces.  "The  Atlas 
Ball  Company  of  Philadelphia  tests  the  hands  of  applicants 
for  the  positions  of  inspectors,  with  a  view  to  detecting  acid 
perspiration.  The  hands  of  many  people  affect  a  fine  steel 
surface  seriously.  In  some  cases  breathing  on  steel  dis- 


302  THE  CONTROL  OF  QUALITY 

colors   the   surface.     The  Atlas   Company   also   tests   for 
this."6 

Assuming  that  the  people  engaged  are  well  suited  to  the 
work  in  hand,  it  is  highly  important  to  impress  upon  them 
the  wide  influence  of  the  control  work  they  are  performing. 
In  any  work  of  the  sort  special  attention  should  be  paid  to  a 
standard  technique  for  making  various  measurements. 
Many  errors  which  cause  lack  of  uniformity  may  be  elimi- 
nated if  certain  measurements  are  always  made  in  the  same 
manner.  It  hardly  need  be  added  that  a  part  of  this  warn- 
ing applies  equally  well  to  the  high  cost  of  hurrying.  Swift- 
ness is  one  thing,  and  a  very  desirable  thing,  but  hurrying  has 
no  place  in  work  of  the  sort,  where  one  blunder  will  be  almost 
indefinitely  repeated  when  the  tools  or  gages  get  out  into 
the  shop. 

6  The  Johansson  Journal,  Vol.  I,  No.  i. 


CHAPTER  XVIII 
GAGES  AND   GAGE-CHECKING 

When  Should  Fixed-Dimension  Gages  Be  Used? 

Various  types  of  gages  have  been  developed  for  special 
purposes,  and  in  approaching  any  manufacturing  problem 
where  the  question  of  dimension  is  important  it  must  first  be 
decided  whether  any  special  operation  should  be  controlled 
through  the  use  of  flexible  measuring  instruments,  such  as 
micrometer  calipers,  or  some  special  form  of  gage  in  which 
the  dimension  is  physically  worked  into  the  gage,  usually  in 
permanent  form.  In  each  instance  special  consideration 
should  be  given  to  such  questions  as : 

Which  type  will  give  the  best  results  from  a  mechani- 
cal standpoint? 

Which  is  best  suited  to  use  by  the  available  labor? 

Which  is  the  more  economical,  both  as  to  first  cost  and 
in  use? 

Flexible  measuring  instruments  such  as  micrometer 
calipers  require  greater  skill  in  their  application  and  are 
more  subject  to  personal  errors  due  to  inaccurate  reading  of 
the  scale,  incorrect  remembrance  of  the  dimension,  and  dif- 
ferences in  "feel."  Ordinarily  it  takes  more  time  to  apply 
the  measuring  instrument  than  it  does  to  use  limit  gages 
with  fixed  dimensions.  This  does  not  always  hold  true, 
however,  because  there  are  many  expert  mechanics  who 
take  very  rapid  and  accurate  measurements  with  microm- 
eter calipers.  It  must  be  remembered  also  that  such 
measuring  instruments  are  capable  of  application  to  several 
different  jobs  and,  consequently,  should  be  used  where  the 

303 


304  THE  CONTROL  OF  QUALITY 

quantity  of  work  prohibits  the  making  of  special  gages, 
although  the  recently  developed  commercial  types  of  adjust- 
able limit  gages  obviate  this  difficulty  of  expense  for  many 
applications. 

No  gage,  and  especially  no  measuring  instrument,  should 
be  applied  to  work  in  motion.  To  prevent  this  requires  a 
certain  amount  of  supervision  and  education  of  the  operator. 
It  is  by  no  means  uncommon  to  see  a  skilled  workman  apply- 
ing a  micrometer  caliper  to  work  on  a  grinding  machine  or  a 
lathe  with  the  spindle  still  in  motion.  Frequently,  too,  the 
proper  way  of  holding  and  applying  micrometer  calipers  is 
not  appreciated.  Through  the  courtesy  of  the  Brown  and 
Sharpe  Manufacturing  Company  a  number  of  photographs 
have  been  secured  showing  the  proper  way  of  holding  and 
using  micrometers  of  various  types.  (Figures  4,  5,  51,  and 
60.) 

Fixed-Dimension  Limit  Gages 

Fixed-dimension  gages  without  limits  are  practically  a 
thing  of  the  past.  They  depend  entirely  upon  the  feel  of 
the  operator  and  have  nothing  to  commend  them,  for  even 
their  expense  of  manufacture  is  little  increased  by  making 
a  double  opening,  to  the  limit  sizes  of  the  tolerance. 

There  would  seem  to  be  little  doubt  that  fixed-dimen- 
sion limit  gages  are  mechanically  suitable  for  all  work  that 
ordinary  micrometers  will  handle.  From  the  standpoint  of 
first  cost  their  application  depends  upon  the  quantity  or 
work  to  be  done,  but  since  their  use  requires  less  skill  and 
greatly  reduces  the  chance  of  error,  it  is  probable  that  their 
use  will  be  widely  extended. 

Frank  O.  Wells  in  an  article  ]  calling  attention  to  the 
probability  that  the  widespread  use  of  gages  will  be  a  dis- 

1  "Future  of  Gages  in  Manufacturing,"  published  in  the  March,  1920,  issue  of  Industrial 
Management. 


GAGES  AND  GAGE-CHECKING 


305 


N9) 

i 


306  THE  CONTROL  OF  QUALITY 

languishing  feature  in  American  industry,  makes  the  point 
that  "gages  allow  departments  which  cannot  see  each  other, 
which  are  separated  by  walls  or  courts  or  other  departments, 
to  act  in  exact  coordination."  The  following  quotation 
from  his  paper  is  of  special  interest: 

A  workshop  establishing  a  definite  tolerance  system,  in  almost 
every  instance,  unless  the  shop  is  in  serious  condition,  will  find  that 
the  desired  tolerance  will  be  greater  than  has  been  taken  advantage 
of  in  the  great  majority  of  pieces  made  before  a  definite  tolerance 
was  set.  The  installation  of  limit  gages  will  merely  find  and  throw 
out  the  small  minority  of  pieces  which  have  wandered  from  the 
standard  the  mechanics  themselves  set  up,  but  have  no  definite 
means  of  adhering  to.  It  is  the  exceptions  to  the  rule  which  cause 
the  most  bother.  The  gage  cuts  out  the  exceptions. 

In  the  automobile  industry,  which  has  brought  dimen- 
sional control  to  such  a  fine  point,  the  use  of  fixed-dimen- 
sion limit  gages  has  been  widely  extended.  In  the  Packard 
Motor  Car  Company's  factory,  for  example,  over  40,000 
gages  are  in  use.  Throughout  all  divisions  of  the  factory 
limit  gages  are  used  extensively  and  are  set  with  tolerances 
ranging  from  plus  and  minus  0.0005  inch  to  plus  and  minus 
o.oio  inch.  On  tolerances  less  than  plus  and  minus  0.0005 
inch  better  results  are  obtained  by  using  an  amplifying  gage 
or  a  fluid  gage,  as  described  later. 

In  gage  design  both  economy  and  technical  requirements 
point  to  the  advisability  of  using  simple  single-purpose  gages. 
The  use  of  flat  plate  gages,  on  which  several  openings  are 
shown,  has  little  to  recommend  it,  for  almost  always  some 
one  of  the  dimensions  will  show  greater  wear  than  the  others, 
so  that  if  the  gage  is  to  be  saved  for  future  use  this  opening 
must  be  peened.  The  appearance  of  the  gage  is  thus  de- 
stroyed, and,  as  everyone  knows,  no  battered -up  gage  ever 
receives  the  same  respect  from  the  user,  as  one  in  perfect 
condition. 


GAGES  AND  GAGE-CHECKING 


307 


Adjustable  Limit  Gages 

There  are  several  types  of  adjustable  limit  gages  on  the 
market  which  permit  the  economical  extension  of  what  are 
practically  fixed-dimension  limit  gages.  (See  Figures  52 
and  54,  showing  the  general  features  of  the  Johansson  adjust- 


Figure  71.     Adjustable  Limit  Snap  Gages — Pratt  and  Whitney  Type 

able  limit  gages,  both  snap  and  plug;  also  Figures  71  and 
72,  showing  similar  information  for  the  Pratt  and  Whitney 
gages.) 

The  wide  anvil  gage  is  coming  into  greater  use  and  has 
very  much  to  recommend  it,  not  only  because  of  decreased 
wear  but  because  the  greater  bearing  surfaces  tend  toward 
more  accurate  results.  Attention  is  invited  to  a  similar 
economy  in  the  use  of  plug  gages  with  reversible  ends  which 


308 


THE  CONTROL  OF  QUALITY 


Figure  72.     Adjustable  Limit  Plug  Gages  with  Reversible  Ends — Pratt  and 

Whitney  Type 


GAGES  AND  GAGE-CHECKING  309 

permit  a  longer  useful  life.  (See  Figure  72.)  The  fact  that 
ends  are  removable  is  advantageous,  as  the  " no-go"  end 
always  wears  less  than  the  other. 

Multiplying  Gages 

It  is  an  interesting  fact  that  in  the  application  of  close 
limit  gages  there  may  be  a  difference  of  as  much  as  20  per 
cent  or  more  in  the  number  of  pieces  passed  by  the  inspector, 
depending  upon  his  mental  attitude  and  material  surround- 
ings. Very  slight  actual  differences  may  thus  become  very 
great  quantitatively.  A  purchaser's  inspector  may  differ 
very  decidedly  from  the  factory  inspector  in  the  use  of  the 
same  gage.  This  fact  alone  accounts  for  the  increasing  use 
of  gages  in  which  such  small  differences  are  enhanced  or 
magnified  to  a  point  where  measurement  becomes  imper- 
sonal. Where  the  work  warrants  the  expense,  the  use  of 
such  gages  is  almost  always  desirable  for  better  work,  and 
especially  so  when  it  is  necessary  to  use  less  skilful  help  and 
to  obtain  a  greater  assuredness  of  results  with  such  help. 
The  Packard  practice,  for  example,  has  developed  that  for 
tolerances  less  than  plus  and  minus  0.0005  inch  much  greater 
certainty  is  obtained  by  using  an  amplifying  gage  or  the 
Prestwich  fluid  gage.  Figure  38  shows  a  photograph  of  an 
operator  using  a  Prestwich  fluid  gage  on  piston  pins,  the 
size  of  which  is  held  to  plus  zero  and  minus  0.000,25  inch. 
These  gages  are  set  from  a  "  master  "  and  are  checked  against 
the  ''master"  after  every  100  pieces.  The  gages  are  used 
in  both  production  and  inspection  on  such  work,  and  at 
times  it  has  been  found  that,  if  the  work  is  held  to  a  closer 
limit  than  plus  or  minus  0.0005  inch,  the  operator  will  hug 
the  high  limit  for  fear  of  getting  the  pieces  undersize.  With 
fixed  gages  on  work  of  this  kind,  the  points  or  anvils  will 
wear  quite  rapidly  and  as  a  result  crib  inspection  would 
show  about  25  per  cent  of  the  pieces  oversize. 


310  THE  CONTROL  OF  QUALITY 

The  principal  types  of  multiplying  gages  are  as  follows: 

1 .  The  multiplying  lever  type.     With  this  type  of  gage 
it  is  important  to  avoid  backlash  or  slip  by  keeping  the 
chain  of  levers  under  pressure  from  one  direction  in  order 
that  the  spring  or  other  tension  device  may  quickly  restore 
the  parts  to  the  zero  measuring  position.     The  points  of 
juncture  in  the  link  work  are  important.     Flexible  tape 
connectors  or  conical  pointed  ends  in  conical   hollows  are 
desirable  for  great  accuracy,  but  wear  must  be  provided 
against  with  care.     All  gages  of  this  type  should  have  posi- 
tive adjustment  for  the  zero  point  and  should  be  provided 
with  standard  test  pieces. 

2.  Dial  indicators  may  be  used  to  accomplish  the  same 
purpose  of  multiplying  errors  (see  Figure  36),  and  so  may 
the  micrometer  heads  which  are  commercially  obtainable. 

3.  The  amplifying  gage  (Figure  69),  and  the  fluid  gage 
(Figure  38),  which  are  primarily  multiplying  comparators. 
These  also  are  suitable  for  use  in  this  connection,  as  has 
been  stated  heretofore. 

4.  Flush  pin  gages.    These  are  made  to  utilize  the  tactile 
sense  for  the  detection  of  small  differences,  as  the  finger-tip 
is  very  sensitive  and  is  able  to  feel  very  small  errors.     Their 
use  should  be  restricted,  however,  to  work  on  which  other 
less  complicated  devices  are  unsuited. 

Special  Gages 

Special  situations  may  be  handled  by  various  designs  of 
gages  and  measuring  instruments,  in  which  there  is  room  for 
the  greatest  ingenuity  and  resourcefulness  of  the  gage  de- 
signer. These  include  such  devices  as  special  testing  fix- 
tures, (e.g.,  as  used  for  measuring  cam-shafts,  etc.);  con- 
tour, profile,  or  outline  gages,  and  so  on. 

It  is  often  useful,  in  drop  forge  work,  to  provide  hot 
gages  for  checking  forgings  more  promptly.  In  such  gages 


GAGES  AND  GAGE-CHECKING  311 

allowance  is  made  for  expansion  of  the  work  while  hot. 
Another  method  is  to  keep  the  gage  hot  and  to  fit  an  insu- 
lated handle  to  it. 

Modern  methods  of  thread-gaging  have  developed  a 
great  many  special  devices,  including  the  use  of  the  optical 
lever  in  projection  apparatus.  A  number  of  these  special 
devices  are  treated  in  detail  in  Chapter  XIX. 

Gage  Tolerances 

The  economical  use  of  gages  requires  that  even  greater 
care  be  given  to  setting  the  tolerances  on  the  dimensions  of 
the  gages  themselves,  than  for  the  work.  Speaking  mathe- 
matically, this  process  is  like  the  second  differential,  in 
which  the  tolerance  for  the  work  is  the  first  differential. 
With  adjustable  gages  the  matter  of  wear  is  easily  disposed 
of,  but  there  are  many  instances  in  which  the  task  is  not  so 
simple.  As  a  general  guide  the  rule  is  sometimes  followed 
of  allowing  a  gage  tolerance  equal  to  10  per  cent  of  the  tol- 
erance for  the  work  proper.  It  is  good  practice  to  make 
limit  plug  gages  0.0002  inch  full  on  the  "go"  end  to  allow 
for  wear,  since  the  "  go  "  end  of  any  gage  wears  much  more 
rapidly  than  the ' '  no-go ' '  end .  Copper  plating  is  sometimes 
resorted  to,  in  order  to  build  up  the  wearing  surface  for  gage 
anvils.  It  is  good  practice  in  many  instances  to  have  a 
systematic  plan  for  replacing  worn  working  gages  with  worn 
inspection  gages. 

The  Application  of  Gages 

Investigation  will  reveal  that  there  is  a  great  field  for 
educating  workers  in  the  use  of  gages.  Special  attention 
should  be  given  to  gage  instruction  cards  (see  Figure  49, 
showing  a  portion  of  one  such  card  as  used  in  the  Lin- 
coln Motor  Company's  factory).  The  technique  necessary 
for  accurate  application  of  gages  demands  separate  study 


312  THE  CONTROL  OF  QUALITY 

and  there  is  undoubtedly  great  room  for  development  of 
motion  study  in  this  work.  More  gages  should  be  mounted 
upon  flexible  stands  which  will  permit  the  gage  to  adjust 
itself  readily  to  the  work  as  well  as  allow  the  operator  to  use 
both  hands. 

Gage-Checking 

The  use  of  limit  gages  brings  with  it  a  special  problem  of 
co-ordination.  In  a  large  factory  using  thousands  of  gages 
there  is  every  need  for  the  intensive  and  practical  applica- 
tion of  systematic  methods  in  gage-checking.  Troublesome 
gages  and  gages  subjected  to  hard  usage  should  be  checked 
very  frequently  indeed.  As  a  general  rule  gages  with  limits 
of  plus  or  minus  one-quarter  thousandth  should  be  checked 
at  least  twice  a  week,  those  with  limits  of  plus  or  minus  one- 
half  thousandth  at  least  once  a  week,  and  those  with  limits 
of  over  one-thousandth,  at  least  once  a  month.  In  addi- 
tion, to  provide  against  accidental  errors,  all  of  the  devices 
for  catching  such  errors  should  be  utilized.  These  have 
been  listed  in  detail  in  Chapter  IV,  pages  60  and  61. 

Naturally  a  problem  of  this  sort  requires  that  the  individ- 
ual gages  be  numbered,  that  there  be  a  card  catalogue  sys- 
tem and  a  tickler  file,  and,  more  important  still,  that  some 
responsible  individual  be  charged  with  the  duty  of  following 
up  this  work.  This  control  of  dimension  of  course  proceeds 
from  the  dimensional  control  laboratory  referred  to  in  the 
preceding  chapter.  The  work  will  be  more  easily  controlled 
if  handled  entirely  through  the  inspection  department  and 
if  all  working  gages  are  issued  from  inspection  centers 
throughout  the  plant,  whether  they  be  central  inspection 
groups  or  merely  the  offices  of  department  inspectors. 

As  noted  before,  the  fact  that  gages  wear  makes  it 
necessary  to  provide  a  chain  of  checking  devices  reaching 
from  the  working  gage  (which  is  subject  to  the  most  wear) 


GAGES  AND  GAGE-CHECKING  313 

back  to  some  master  gage  template  or  standard  measuring 
machine  which  is  subject  to  extremely  little  wear  and,  there- 
fore, reasonably  sure  of  remaining  constant.  The  number  of 
links  in  this  chain  is  frequently  dependent  upon  the  number 
of  times  the  working  gages  are  to  be  applied  and  upon  their 
relative  wear.  Thus,  for  a  very  close  dimension,  a  soft  steel 
or  even  a  hard  steel  template  might  be  applied  by  an  expert 
in  1,000  checkings  without  serious  wear.  Then  in  such  a 
case,  if  the  quantity  of  work  contemplated  more  than  1,000 
checkings  or  applications  of  the  template,  we  should  have 
to  construct  one  more  link  in  the  chain  in  order  to  have 
something  to  check  the  template. 

In  building  up  this  chain  for  dimensional  control  several 
terms  have  been  employed,  but  there  is  no  set  of  definitions 
in  general  use.  The  definitions  recommended  in  the  Prog- 
ress Report  of  the  Committee  on  Limits  and  Tolerances  in 
Screw  Thread  Fits,  as  published  in  Mechanical  Engineering, 
August,  1918,  are: 

Master  Gage.  A  gage  which  is  kept  as  a  standard  solely  for  com- 
paring reference  gages. 

Reference  Gage.  A  gage  used  by  the  manufacturer  and  by  which 
the  workman's  gage  is  tested.  A  copy  of  the  master  gage. 

Standard  Gage.     The   English   term   for   Master  Gage. 

Shop  or  Workman's  Gage.  A  gage  used  by  the  workman  in 
everyday  practice.  It  is  tested  by  or  with  the  Reference  Gage. 

The  above  definitions  are  a  sufficient  guide  for  ordinary 
purposes,  but  many  gages  will  be  checked  with  greater  ease 
if  they  are  provided  with  close-fitting  templates  as  an  addi- 
tional step  in  the  chain.  Further,  for  straight  dimensional 
work  (that  is,  excluding  special  shapes,  such  as  screw  threads 
and  profiles)  several  of  the  early  steps  in  the  chain  of  control 
gages  may  be  eliminated  by  the  use  of  Swedish  gage  blocks. 
The  basic  principle,  however,  must  be  observed  with  care: 
One  master  set  of  blocks  should  be  retained  solely  for  checking 


3H  THE  CONTROL  OF  QUALITY 

the  other  sets  of  blocks  which  are  used  in  the  direct  dimensional 
checking  of  gages  and  tools. 

The  Slip  in  Transferring  Size 

Another  chain  of  error  arises  in  the  possibility  of  slip  in 
passing  from  dimension  to  dimension.  With  the  feeling 
that  the  Johansson  Company's  experience  in  the  matter  of 
making  fine  adjustments  would  be  of  interest  in  this  respect, 
they  were  asked  for  their  opinion  on  the  matter.  The  follow- 
ing information  was  furnished  by  C.  E.  Johansson,  Inc. 
through  the  courtesy  of  Huber  B.  Lewis,  Vice-President: 

It  is  possible  to  transfer  size  without  any  observable  slip.  We 
do  it  regularly  in  our  laboratory  work.  Our  checking  instruments 
are,  of  course,  of  extreme  delicacy  and  we  are  dealing,  in  most  cases 
with  surfaces  of  extremely  accurate  finish^  It  seems  to  us  that  the 
amount  of  slip  which  might  occur  in  the  practical  application  of 
measuring  implements  depends,  first  upon  the  sensitiveness  and  the 
uniform  accuracy  of  the  comparator,  and  second  upon  the  finish 
of  the  surfaces  being  compared.  As  an  illustration:  if  a 
comparator  were  set  by  using  a  standard  plug  with  a  fine  lapped  sur- 
face, a  ground  part  checked  on  this  comparator  would  probably 
register  large  because  of  the  surface  irregularities.  A  clearer  com- 
parison might  be  the  slip  between  the  plug  templet  and  a  ring  made 
to  fit  this  templet.  In  practical  tests  we  have  made  on  plugs  and 
rings  I "  in  diameter,  we  find  that  a  clearance  of  approximately  .0001" 
should  be  allowed  in  order  for  the  plug  to  enter  the  ring  with  a  nice 
wringing  fit.  Actual  measurement  would,  therefore,  show  the  ring 
to  be  .0001"  larger  than  the  plug  to  which  it  was  fitted  which  would 
probably  establish  for  practical  purposes,  a  slip  in  measurement  of 
.0001".  By  using  extreme  care  in  the  finish  of  the  surfaces  of  the 
plug  and  ring,  paying  particular  attention  to  roundness,  this  slip 
can  be  reduced  to  .00005"  and  the  plug  inserted  in  the  ring  without 
using  force.  On  the  other  hand,  a  clearance  of  more  than  .0001" 
would  be  required  if  the  plug  or  ring  were  not  round  and  smooth. 

Two  Johansson  Standard  Gage  Blocks  can  be  checked  against 
each  other  where  the  slip  would  not  exceed  .00001".  Take  two  new 
i"  blocks  which  are  exactly  alike  within  .ooooi"or  better,  wr  ng  end- 
radius  jaws  on  one  block ;  the  other  block  can  be  inserted  in  the  recess 


GAGES  AND  GAGE-CHECKING 


315 


between  the  extension  jaws  so  that  it  will  remain  in  place  when  sus- 
pended, through  the  niceness  of  fit.  It  may  be  said  that  some  slip 
occurs  in  the  union  between  the  first  block  and  the  end  pieces  due  to 
the  filament  of  oil  or  moisture  between  the  surfaces;  whatever  that 
slip  may  be,  if  at  all  appreciable,  will  also  exist  between  the  jaws  and 
the  second  block  when  it  is  inserted  between  the  extension  pieces. 
This  would  also  be  true  in  rougher  work,  for  instance,  a  snap  gage 
set  to  a  templet.  Assuming  that  some  slip  occurs  in  mating  the 
snap  gage  to  the  templet,  a  corresponding  slip  would  occur  between 


Figure  73.     Pratt_and  Whitney  Taper  Gages 

the  snap  gage  and  the  parts  checked  by  it  so  that  the  parts  would 
correspond  very  closely  with  the  original  templet. 

Mr.  Johansson  illustrates  this  principle  of  fit  in  a  very  interest- 
ing way.  He  takes  a  i"  Standard  Gage  Block  with  the  radius  jaws 
extending  down  each  side  and  stands  the  block  on  the  table  before 
him.  By  the  side  of  the  block  he  stands  a  i"  plug  gage,  finished  to 
the  same  degree  of  accuracy  as  the  standard  block.  After  making 
sure  that  both  pieces  are  of  the  same  temperature,  he  inserts  the  i" 
plug  gage  into  the  snap  gage  opening  formed  by  the  i"  block  and  the 
end  pieces.  You  will  note  that  the  surfaces  of  the  plug  gage  and  the 
extension  pieces  are  in  contact  only  along  a  hair  line  on  each  side. 
Notwithstanding  the  slightness  of  this  contact,  the  fit  is  sufficiently 
nice  to  permit  Mr.  Johansson  to  raise  the  entire  combination  by 
lifting  the  end  of  the  plug  gage. 


316  THE  CONTROL  OF  QUALITY 

Mr.  Johansson  then  takes  the  standard  block  combination  and 
holds  it  in  his  hand  while  he  counts  five  slowly.  The  plug  gage  is 
again  inserted  and  this  time  it  is  impossible  to  lift  the  standard  block 
combination  with  the  plug  due  to  the  expansion  of  the  block.  The 
plug  is  then  held  in  the  hand  while  he  again  counts  five,  thus  bring- 
ing the  plug  approximately  to  the  same  temperature  as  the  block 
again  and  this  time  the  fit  is  the  same  as  it  originally  was  and  it  is 
possible  to  lift  the  standard  block  combination  by  lifting  the  end  of 
the  plug.  The  amount  of  expansion  would,  of  course,  depend  upon 
the  difference  between  the  body  temperature  and  the  temperature 
in  the  room  where  the  experiment  is  performed,  but  the  change 
would  not  account  for  more  than  two  or  three  hundred  thousandths 
of  an  inch,  perhaps,  and  this  again  illustrates  the  very  small  amount 
of  slip  that  may  occur  when  surfaces  of  equal  finish  are  compared. 

After  every  precaution  has  been  taken  to  see  that  the 
proper  gages,  correctly  checked  from  time  to  time  and  kept 
to  dimension,  are  provided,  and  even  if  they  are  properly 
used,  there  still  remains  much  to  be  done  if  precise  work  is 
to  be  secured  with  certainty.  For  this  reason  in  Chapter 
XX  will  be  found  some  comments  on  the  points  to  be  ob- 
served in  precision  processes,  as  well  as  data  indicating 
the  present  state  of  the  machining  art  in  the  matter  of 
dimensional  accuracy. 

Chapter  XIX  is  devoted  to  the  presentation  of  the  very 
special  and  intricate  business  of  screw  thread  production 
and  gaging.  Many  of  the  devices  and  methods,  however, 
are  more  generally  applicable  to  irregular  outlines,  contours, 
and  forms. 


CHAPTER  XIX 
THREAD-GAGING1 

Evolution  of  Thread-Gaging 

The  evolution  of  thread-gaging  is  an  epitomized  history 
of  all  gage  development,  beginning  with  simple  ring  and 
plug  gages  and  micrometer  calipers  and  then  running  the 
gamut  through  a  long  series  of  specialized  measuring  and 
checking  devices  up  to  the  use  of  the  latest  methods  of  opti- 
cal projection.  This  array  of  equipment  and  the  great  and 
continued  effort  of  many  expert  engineers  involved  in  its 
creation,  is  warranted  by  the  value  of  the  screw  thread  as 
an  element  of  mechanism  and  is  made  necessary  by  the  diffi- 
culties inherent  in  accurate  thread-making. 

The  beneficial  influence  of  munition  and  automotive 
requirements  are  clearly  traceable  in  this  evolution.  More 
perfect  interchangeability  without  sacrifice  of  dependa- 
bility or  strength  in  relation  to  weight  have  operated  to  en- 
hance the  importance  of  precision  in  the  manufacture  of 
threaded  parts.  In  fact  these  characteristics  have  been 
greatly  improved,  with  corresponding  improvement  in  the 
apparatus  for  controlling  their  quality  in  manufacturing. 

So  great  a  variety  of  gaging  devices  is  now  available  as  a 
result  of  the  recent  intensive  development  just  mentioned, 
that  the  first  practical  problem  encountered  in  building  up 
a  control  system  for  threaded  work  is  the  selection  of  appa- 
ratus sufficiently  positive  in  effectiveness  without  being  too 
cumbersome  or  complicated.  It  is  very  easy  indeed  to  build 
up  a  long  chain  of  control  from  the  working  gage  through 


1  The  author  is  indebted  to  the  Honorable  James  Hartness,  Governor  of  the  State  of  Ver- 
mont (and  formerly  President  of  the  Jones  and  Lamson  Machine  Company  of  Springfield,  Vt.) 
for  his  kindness  in  furnishing  much  of  the  material  presented  in  this  chapter. 

317 


31 8  THE  CONTROL  OF  QUALITY 

inspection,  reference,  and  master  gages  with  their  check 
templates,  up  to  final  master  models.  But  the  ramifica- 
tions thus  introduced  are  all  potential  sources  of  error  and 
necessitate  solicitous  watching. 

Anything  that  can  be  done  without  sacrificing  efficiency 
to  reduce  this  complexity  by  shortening  the  chain  between 
the  work  itself  and  the  final  control  equipment  is  highly  de- 
sirable for  many  and  very  apparent  reasons.  It  has  been 
shown  already  how  the  chain  may  be  shortened  in  simple  or 
single  dimensional  work  by  the  use  of  Johansson  block 
gages.  It  is  now  proposed  to  show  how  the  same  thing 
results  in  precise  thread  control  from  the  use  of  modern 
optical  projection  apparatus. 

Again  quoting  L.  P.  Alford's  frequent  statement,  "The 
purpose  of  industry  is  to  make  goods,"  thread-gaging  devices 
are  of  no  value  for  their  own  sake,  but  merely  as  a  means  for 
assuring  the  production  of  threaded  parts  in  accordance 
with  the  desired  standards.  The  more  direct  and  simple 
such  devices  can  be  made  the  better,  but  the  first  step,  as 
always  in  the  control  of  quality,  is  to  study  the  product,  the 
errors  which  enter  into  its  production,  the  causes  of  these 
errors,  and  the  means  of  regulating  the  manufacturing  proc- 
esses where  errors  are  made. 

In  the  analysis  of  screw-thread  elements  essential  to 
strength  and  dependability,  James  Hartness  states:2 

On  account  of  the  vagueness  of  our  general  knowledge  of  the 
conditions  under  which  it  takes  its  stress,  we  frequently  underesti- 
mate the  importance  of  the  screw,  and,  through  ignorance,  continue 
practices  that  greatly  increase  the  hazard  of  life  in  travel  by  rail, 
•  automobile  or  airplane,  as  well  as  lessen  the  reliability  of  perform- 
ance of  other  pieces  of  machinery.  A  screw-thread  fastening  is  very 
dependable  if  the  two  component  parts  are  properly  fitted. 

While  it  is  not  possible  to  attain  perfection  in  this  work,  an 
analysis  of  the  various  elements  that  are  essential  for  strength  and 


1  "Optical  Projection  for  Screw-Thread  Inspection"  in  Mechanical  Engineering,  Feb. 


THREAD-GAGING  319 

dependability,  and  the  reduction  of  weight,  will  greatly  simplify  our 
efforts  and  make  it  possible  to  attain  a  point  much  nearer  per- 
fection. 

Briefly  stated,  a  screw's  reliability  depends  upon  the  following 
elements: 

A  Material 

B  Form  of  profile  of  the  thread 

C  Diameter  of  the  screw 

D  Lead  or  number  of  threads  per  inch. 

After  the  foregoing  general  characteristics  have  been  deter- 
mined, we  must  consider  the  following  details  which  depend  on  the 
methods  and  skill  employed  in  production : 

1  Smoothness  and  density  of  surface 

2  Fit,  which  relates  particularly  to  the  exact  relationship  of 

the  size  of  the  two  component  parts 

3  Precision  of  lead,  which  relates  to  the  precision  of  advance 

of  the  helix  or  degree  of  precision  with  which  the 
number  of  threads  per  inch  are  made 

4  Uniformity  or  steadiness  of  advance  of  helix 

5  Form,  relating  to  contour  of  a  single  thr  ad 

6  Roundness,  as  relating  to  the  circular  path  of  the  helix 

7  Parallelism  or  taper. 

These  elements  are  all  inter-related. 

Inter-relation  of  Thread  Elements 

The  last  sentence  is  particularly  significant.  Before 
threading,  the  problems  of  ordinary  cylindrical  or  tapered 
work  are  encountered,  such  as  maintaining  diameters,  round- 
ness or  concentricity,  and  parallelism.  These  difficulties 
are  carried  over  into  the  threading,  where  they  are  accentu- 
ated by  the  creation  of  spiral-warped  surfaces  which  add  the 
complications  of  pitch  or  lead  of  the  screw,  the  angular 
form  of  the  thread,  and  several  diameters  instead  of  one. 
Thus  errors  accumulate  in  three  dimensions.  In  the  case 
of  a  single  screw  thread  considered  alone  the  inter-relation 
of  errors  must  be  carefully  taken  into  account ;  for  example, 


320 


THE  CONTROL  OF  QUALITY 


Figure  74.     An  Exaggerated  Form  of  Stud 

To  illustrate  the  fact  that  when  there  is  a  difference  in  lead  between  the  screw  and 
the  nut  or  threaded  hole  the  middle  threads  do  not  touch  either  in  the  gage  or  the 
work  until  the  opposing  end  threads  are  crushed.  It  also  illustrates  the  conflict 
between  the  stresses  at  the  two  ends  of  the  engagement.  Courtesy  Jones  and  Lamson 
Machine  Company. 


THREAD-GAGING  321 

a  variation  in  pitch  may  involve  a  much  greater  error  in 
effective  diameter. 

When  the  investigation  of  inter-related  errors  in  screw 
threads  is  extended  to  include  mating  parts,  as  it  ultimately 
has  to  be  in  every  case,  the  percentage  feature  of  precision 
is  involved  because  the  error  in  the  lead  of  the  thread  varies 
with  the  length  of  the  thread.  The  possibilities  in  the  latter 
case  are  well  illustrated  in  Figure  74. 

The  preceding  general  discussion  of  the  elements  of 
threads  and  their  accompanying  errors  assumes  theoreti- 
cally smooth  surfaces.  In  practice,  however,  the  surfaces 
of  threads  are  not  smooth,  nor  are  edges  continuous  lines 
and  true  curves.  The  manufacturing  processes  inevitably 
leave  their  marks  in  the  form  of  irregularities,  chips,  and  so 
on,  which  vary  in  magnitude  with  the  character  of  the  work. 
No  matter  how  slight  these  irregularities,  their  effect,  singly 
or  collectively,  is  to  increase  errors  of  gaging  or  measuring. 

It  is  not  the  purpose  of  this  book  to  go  into  the  techni- 
calities of  the  various  features  of  design,  and  it  is  assumed, 
therefore,  that  the  design  provides  for  safe  clearances  be- 
tween mating  parts,  especially  bottom  and  outside  clear- 
ances. It  is  assumed  also  that  the  design  provides  for 
normal  wear  of  cutting  tools,  especially  at  the  points  and 
edges  where  wear  may  ordinarily  be  expected  to  reach  its 
maximum  effects.  With  these  assumptions,  then,  we  are 
chiefly  concerned  with  the  remaining  factors  of  lead,  pitch- 
diameter,  and  slope  or  angle.  The  first  two  usually  require, 
and  in  fact  warrant,  the  most  attention.  Their  inter-rela- 
tion is  such  that  lead,  especially  in  long  screws,  is  of  para- 
mount importance. 

Working  Thread  Gages 

The  usual  gages  for  inspecting  threaded  parts  in  the  shop 
are  of  the  well-known  plug  and  ring  type  (see  Figures  75  and 

21 


322 


THE  CONTROL  OF  QUALITY 


76) .  A  series  of  similar  gages  can  be  made  for  gaging  the 
various  elements  of  the  thread  separately,  but  it  would 
hardly  be  wise  or  worth  while  to  furnish  such  a  series  as 
working  gages  or  even  as  inspection  gages  for  use  in  the 
shops.  Consequently  the  use  of  several  gages  for  such  work 
finds  little  application  outside  of  the  tool-room  in  thread- 
chasing.  The  gaging  system  for  practical  shop  use,  there- 
fore, reduces  to  limit  threaded  plug  and  ring  gages  which 
gage  all  essential  elements  at  once.  .  This  involves  for  the 
threaded  hole: 

(a)  Threaded  "go"  plug  of  a  length  equal  to  the  longest  en- 
gagement of  work 


Figure  75.     Typical  Thread  Gages — Pratt  and  Whitney  Company 


THREAD-GAGING 


323 


(b)  Threaded  "not  go"  plug,  made  short  and  with  clearance 
for  full  and  root  diameters; 

and  for  bolt  or  screw: 

(a)  Threaded  "  go  "  ring  of  a  length  equal  to  the  longest  engage- 
ment of  work 

(b)  Threaded  "not  go"  ring  made  short  and  with  clearance 
for  full  and  root  diameters.3 


The  Hartness  Comparator 

Now,  the  fact  is  that  such  gages  are  blind  in  the  sense 
that  the  gage  covers  the  work  while  the  latter  is  being  gaged, 

and  knowledge   must   be      _  

based  upon  the  feel  of  the 
fit  of  the  gage  with  the 
work.  This  might  do  well 
enough  were  it  not  for  the 
fact  that  the  work  inevi- 
tably carries  with  it  the 
little  errors  already  re- 
ferred to,  such  as  rough- 
ness of  the  surfaces,  chips, 
and  slight  variations  or 
wabbles  in  the  pitch,  in 
addition  to  direct  dimen- 


Figure    76.     Typical    Thread    Gage — 
Pratt  and  Whitney  Company 


sional  variations  which  are  always  present.  These  hidden 
dangers  are  without  doubt  at  the  root  of  most  of  the 
aggravating  and  perplexing  troubles  so  frequently  en- 
countered in  the  assembling  of  threaded  parts,  troubles 
which  are  augmented  in  marked  degree  with  increase 
in  the  precision  required  for  neat  fits  and  complete  inter- 
changeability.  Owing  to  the  conditions  just  set  forth,  the 
use  of  snap  and  ring  gages  actually  discards  some  of  the  best 


3  "Progress  Report  of  Committee  on  Limits  and  Tolerances  in  Screw-Thread  Fits,"  Me- 
chanical Engineering,  Aug.,  1918. 


324 


THE  CONTROL  OF  QUALITY 


threaded  parts  of  a  lot  and  accepts  some  of  the  worst.  Con- 
sequently, even  with  gages  in  excellent  shape,  it  is  important 
to  base  our  control  system  on  the  work  itself,  since  gages  of 


Figure  77.     General  View  of  Hartness  Screw  Thread  Comparator 

this  type  are  apt  to  be  misleading.  Furthermore,  it  is  not 
enough  to  know  that  errors  exist  because  we  can  feel  them ; 
they  must  be  brought  out  into  the  open  and  measured  be- 
fore we  can  proceed  to  correct  them  with  any  degree  of 
assurance  as  to  final  results.  Several  designs  of  optical 


Figure  78.     Another  General  View  of  Hartness  Screw  Thread  Comparator 

projection  apparatus  have  been  developed  for  this  purpose, 
both  in  this  country  and  abroad,  and  these  mark  a  decided 
advance  in  apparatus  for  checking  both  threaded  work  and 
thread  gages. 

The  Hartness  screw  thread  comparator,  illustrated  in 
Figures  77  and  78,  positions  the  work  in  a  cradle  or  work- 


THREAD-GAGING  325 

holder  (see  Figure  79) ,  in  such  a  relation  to  its  helix  and  diam- 
eter as  to  show  the  situation  at  a  glance,  by  visual  com- 
parison of  the  projected  outline  or  shadow  with  the  tolerance 
chart  of  the  screen. 

Internal  threads  may  be  checked  with  the  same  appara- 


Figure  79.     The  Work  Holder  and  Projection  Lens  of  Hartness  Screw  Thread 

Comparator 

Showing  a  standard  plug  in  the  cradle.      The  machine  is  adjusted  by  use  of  a  standard  threaded 
plug.     The  plug  is  a  perfect  check  that  may  be  used  during  the  run  of  gaging. 

tus  by  the  use  of  sulphur  casts,  after  the  method  long  in  use 
in  measuring  the  cartridge  chambers  of  small  arms.  Graphite 
may  be  mixed  with  the  sulphur  (7  per  cent  of  graphite  by 


326  THE  CONTROL  OF  QUALITY 

weight)  to  reduce  shrinkage  and  surface  reflection.4  Or,  the 
tap  used  in  threading  the  hole  may  be  checked. 

There  is  then  made  available  a  simple  means  for  verify- 
ing threaded  work  (both  passed  and  rejected  parts),  so  that 
errors  may  be  revealed  and  measured.  This  apparently  is 
the  proper  starting  point  for  bringing  the  work  under  con- 
trol. The  same  procedure  is  then  extended  to  correct  the 
tool  equipment  so  that  it  will  produce  work  of  the  desired 
character ;  and  finally  to  check  such  gages  as  are  needed  for 
convenience,  being  guided  always  by  the  principle  that  it  is 
more  useful  as  a  measure  of  a  gage's  effectiveness  to  check 
the  work  which  the  gage  passes  than  it  is  to  regard  the 
absolute  measurement  of  the  various  elements  of  the  gage 
proper  as  final  and  conclusive. 

It  may  be  mentioned  incidentally  that  there  is  a  useful 
field  of  application  for  projection  apparatus  in  irregular 
profile  and  contour  work,  as  well  as  for  threads;  but  in  all 
work  with  such  equipment  due  attention  must  be  given  to 
locating  the  apparatus  away  from  troublesome  vibrations. 

Other  Equipment  for  Measuring  Threads 

For  a  complete  description  of  the  equipment  employed 
by  the  Bureau  of  Standards  in  measuring  thread  gages,  the 
reader  is  referred  to  the  paper  by  H.  L.  Van  Keuren,  men- 
tioned above,  which  may  be  used  as  a  guide  in  equipping 
the  control  laboratory  for  thread  gage-checking.  The 
gaging  system  should  be  adopted  with  reference  to  the 
character  of  the  work  to  be  handled.  For  precise  work  the 
optical  projector  will  usually  be  supplemented  by  a  special 
lead  testing  machine.  An  excellent  instrument  of  this  type 
was  brought  to  a  high  state  of  perfection  during  the  war  by 
Major  H.  J.  Bingham  Powell,  who  was  Director  of  the  Joint 
Gage  Laboratories  of  the  British  War  Mission  and  the 

<  "The  Measurement  of  Thread  Gages,"  by  H.  L.  Van  Keuren,  chief  of  Gage  Section, 
United  States  Bureau  of  Standards,  in  Mechanical  Engineering,  Nov.,  1918. 


THREAD-GAGING  327 

United  States  Bureau  of  Aircraft  Production.  For  such 
work  the  West  and  Dodge  Company's  lead  tester  (see  Figure 
8)  is  often  found  in  the  dimensional  control  rooms  of  fac- 
tories doing  precise  work.  Similarly,  the  well-known  three- 
wire  method  for  measuring  the  pitch  diameter  should  be 
provided  for  by  supplying  accurate  apparatus  for  this  work. 
The  method  is  a  most  useful  one,  but  requires  careful  appli- 
cation for  accurate  results. 

Ordinary  ring  and  plug  gages  are  frequently  supple- 
mented in  close  work  by  special  types  of  gages,  such  as  com- 
bined lead  and  diameter  gages,  using  micrometer  heads  in 
combination  with  compound  levers  or  dial  indicators  for  en- 
hancing errors  in  the  work — making  them  appear  greater. 
For  simple  work  the  ordinary  type  of  screw  thread  microm- 
eter still  has  a  useful  field. 

Thread  Gage  Tolerances 

There  probably  is  no  other  branch  of  gaging  which  re- 
quires so  much  attention  to  the  effect  of  wear  as  does  accu- 
rate thread-gaging,  and  this,  of  course,  brings  in  the  matter 
of  gage  tolerances.  In  this  connection  Frank  O.  Wells5 
states : 

One  great  difficulty  with  the  business  of  manufacturing  thread 
gages  is  the  unreasonable  and  useless  accuracy  of  gage  tolerance  and 
wear  allowance  sometimes  requested  by  purchasing  firms.  When  a 
tolerance  of  0.0002  in.  is  set  on  a  gage  specification  it  should  mean 
that  the  customer's  tolerance  on  product  is  as  close  as  o.ooi  in.  If 
the  purchaser's  manufacturing  tolerance  is  any  broader  than  that, 
there  is  no  use  in  keeping  the  gage  so  close.  A  0.0002  in.  error  would 
be  lost  in  the  comparison.  In  order  to  facilitate  the  making  and  to 
lessen  the  cost  of  thread  gages,  it  is  well  to  allow  quite  liberal  toler- 
ances in  their  manufacture,  and  we  recommend  the  following  as 
being  applicable  for  most  cases  where  medium  tolerances  are 
allowed  on  product: 

5  "Present  Practice  in  Thread  Gage  Making."  by  Frank  O.  Wells,  President,  Greenfield 
Tap  and  Die  Corporation;  member  Congressional  Screw  Thread  Commission,  in  Mechanical 
Engineering,  Dec.,  1918. 


328  THE  CONTROL  OF  QUALITY 

From  4  to  6  pitch  allow  a  tolerance  of  0.0006  in.;  from  7  to  18 
pitch  allow  a  tolerance  of  0.0004  m-  5  from  20  to  28  pitch  allow  a  toler- 
ance of  0.0003  in. ;  from  30  to  80  pitch  allow  a  tolerance  of  0.0002  in. 

The  foregoing  applies  to  master  gages.  For  inspection 
gages  the  tolerances  would  be  slightly  wider,  and  would 
begin  where  the  master  inspection  gage  tolerances  leave  off. 
These  would  be  as  follows: 

From  4  to  6  pitch  a  tolerance  of  0.0009  m- 1  from  7  to  10  pitch  a 
tolerance  of  0.0006  in. ;  from  1 1  to  18  pitch  a  tolerance  of  0.0004  in. ; 
from  20  to  28  pitch  a  tolerance  of  0.0003  m-I  from  30  to  40  pitch  a 
tolerance  of  0.0003  in.;  from  44  to  80  pitch,  0.0002  in. 

All  of  the  foregoing  tolerances  would  be  applied  plus  in  the  case 
of  go  male  gages  and  no-go  female  gages ;  and  minus  on  no-go  male 
and  go  female  thread  gages. 

The  plus  and  minus  tolerances  given  apply  to  pitch  diameters 
of  all  thread  gages  and  also  to  root  or  core  diameters  of  templets 
or  female  thread  gages. 

The  maximum,  or  go,  templet  gage  represents  the  maximum  or 
basic  screw  and  its  manufacturing  tolerances  should  be  minus  on 
pitch  diameter  and  root  diameter.  The  minimum  or  no-go,  templet 
should  be  made  to  plus  tolerances  with  an  extra  plus  allowance  on 
the  root  diameter,  which  will  insure  this  gage's  really  checking  the 
effective  size  of  the  screw.  The  wear  and  adjustment  tolerance  on 
a  gage  should  be  coarse  or  fine  on  a  sliding  scale  according  to  the 
manufacturer's  tolerance  on  his  product. 

As  Mr.  Wells  shows,  the  matter  of  gage  tolerances  refers 
back  to  the  tolerances  required  for  the  work  itself.  The 
latter  subject  has  received  much  attention  from  engineering 
organizations  in  recent  years,  and  the  results  of  their  con- 
clusions as  set  forth  in  various  publications  should  have  the 
careful  attention  of  manufacturers. 

Precision  Depends  upon  Service  Requirements 

It  may  be  noted  again  that  the  problems  of  this  subject 
necessitate  at  the  start  a  determination  of  the  things  we 
wish  to  accomplish  with  our  product.  What  service  are 


THREAD-GAGING  329 

the  threaded  parts  required  to  perform?  What  are  the 
elements  of  these  parts  which  make  the  principal  con- 
tribution to  the  rendering  of  such  service?  What  variations 
from  the  ideal  for  the  sake  of  economy  of  manufacture  is  it 
sensible  to  tolerate  without  too  greatly  compromising  effec- 
tiveness? When  the  subject  is  analyzed  in  this  order,  it 
may  readily  develop  that  the  best  results  will  flow  from 
easier  tolerances  but  with  closer  adherence  to  these  standards 
in  the  dimension  and  finish  of  the  product.  Thus  better 
attention  to  the  quality  of  the  work  may  permit  the  gage 
tolerances  to  be  a  fifth  instead  of  a  tenth  of  the  tolerances 
allowed  for  the  work;  especially  when  the  work  is  more 
positively  checked  from  time  to  time  by  independent  meth- 
ods, such  as  by  the  use  of  the  optical  projection  apparatus 
referred  to. 


CHAPTER  XX 
THE   PRECISE   CONTROL   OF   PROCESSES 

What  Dimensional  Precision  Is  Practicable? 

In  the  study  of  dimensional  control  it  is  sometimes  de- 
sirable to  consider  what  degree  of  accuracy  is  commercially 
obtainable  for  a  given  job.  The  logical  starting  point  for 
such  an  investigation  is  the  examination  of  the  results 
obtained  in  various  processes  which  are  in  actual  use  at  the 
time.  It  should  be  observed,  however,  that  any  such  figures 
are  subject  to  correction  from  time  to  time  as  the  manufac- 
turing arts  are  advanced  toward  greater  precision.  To  be 
sure,  a  very  high  degree  of  accuracy  has  been  obtained  in 
certain  businesses  at  the  present  time,  and  it  would  be  diffi- 
cult to  see  any  advantage  at  the  moment  in  further  improve- 
ment; but  experience  shows  quite  clearly  that  progress  has 
not  stopped.  As  the  advantages,  both  commercial  and 
technical,  of  higher  precision  come  to  be  recognized,  there 
is  no  doubt  that  further  and  even  more  startling  advances 
will  be  made. 

The  manufacture  of  automobiles  has  developed  a  very 
high  degree  of  accuracy  on  a  commercial  scale,  so  that  our 
first  examples  of  obtainable  precision  are  taken  from  that 
industry.  In  the  Lincoln  factory,  for  example,  "there  are 
more  than  5,000  operations  in  which  the  deviation  from 
standard  is  not  permitted  to  exceed  the  one  thousandth 
part  of  an  inch,  more  than  1,200  in  which  it  is  not  permitted 
to  exceed  a  half  of  one  thousandth;  and  more  than  300  in 
which  one-quarter  of  a  thousandth  is  the  extreme  limit  of 
tolerance."  The  large  number  of  closely  held  operations  in 
this  industry  has  been  a  matter  of  frequent  and  general 

330 


THE  PRECISE  CONTROL  OF  PROCESSES  331 

comment.  It  is  only  a  year  or  two  since  the  Marmon  Com- 
pany, for  example,  at  the  Motor  Show  in  New  York  put  on 
an  exhibition  in  which  two  men  took  down  and  reassembled 
a  complete  engine  in  I  hour  and  45  minutes.  Such  pre- 
cision kills  the  need  of  hand-fitting. 

Automobile  Experience 

A  former  associate,  G.  D.  Stanbrough  (in  response  to 
the  author's  request),  writes  the  following  setting  forth  his 
experience  with  precision  work  in  the  automobile  industry : 

With  regard  to  commercial  limits  on  different  forms  of  ma- 
chine work  I  may  say  that  at  the  time  a  new  model  is  placed  in  the 
factory l  the  limits  are  carefully  gone  over  by  a  committee  represent- 
ing the  Engineering,  the  Manufacturing  and  the  Inspection  Depart- 
ments. The  committee  sets  the  limits  which  the  Manufacturing 
Department  knows  from  past  experience  are  commercially  possible, 
and  yet  within  the  tolerances  desired  by  the  Engineering  Depart- 
ment. It  is  our  practice  to  give  all  information  necessary  on  the 
drawing,  as  to  roughing  and  finishing  dimensions,  also,  forging  and 
casting  dimensions. 

It  might  be  well  to  point  out  at  this  time  that  an  understanding 
is  not  always  had  as  to  the  matter  of  limits  in  manufacturing.  The 
matter  of  design  and  its  relation  to  limits  is  quite  frequently  mis- 
understood and  much  trouble  can  be  avoided  by  thoroughly  under- 
standing these  functions.  It  should  be  borne  in  mind  that  the  de- 
sign of  a  piece  of  apparatus  involves  the  strength  of  materials  and 
the  appearances.  That  is,  you  must  have  the  necessary  strength  to 
perform  the  function  and  to  have  a  finish  compatible  with  the  con- 
dition under  which  the  piece  is  used,  or  the  particular  ideas  from 
a  sales  policy  that  is  to  be  carried  out.  While  on  the  other  hand  the 
matter  of  limits  is  purely  manufacturing  and  involves  the  practices 
of  the  shop  in  which  the  work  is  done. 

It  naturally  follows  that  as  closer  limits  are  approached  in  man- 
ufacturing, the  design  in  turn  can  be  improved.  An  automobile 
manufactured  to  give  satisfactory  service  over  a  long  life  must  of  ne- 
cessity be  built  to  close  limits.  Noise  probably  more  than  any 
other  one  cause  is  responsible  for  the  comparatively  short  period  of 

The  Packard  Motor  Car  Company's  factory  is  referred  to. 


332  THE  CONTROL  OF  QUALITY 

time  in  which  a  machine  gives  satisfaction  to  the  customer.  In  or- 
der to  manufacture  an  automobile  that  will  give  noiseless  operation 
over  a  period  of  years  close  limits  are  essential,  and  it  has  been  our 
constant  aim  in  designing  tools  and  in  laying  out  our  processes  to 
decrease  our  limits. 

To  date  we  are  able  to  hold  the  grinding  on  such  parts  as  the 
piston  pin,  the  cam  roller  pin,  and  other  parts  subject  to  reciprocat- 
ing motion  to  a  limit  of  plus  .000  minus  .00025.  ^  e  are  holding 
turning  dimensions  to  plus  or  minus  .0005 — this  limit  being  held  on 
bushings  and  bearings.  On  milling  work  we  are  holding  to  plus  and 
minus  .001,  in  fact  we  have  a  4^2  "  dimension  on  our  crankcase  which 
is  held  to  this  limit.  On  milling  key -ways  we  hold  the  width  to  a 
limit  of  plus  or  minus  .0005.  On  reamed  work  we  hold  to  a  limit  of 
plus  or  minus  .0005  with  the  exception  of  the  cramshaft  sprocket, 
the  piston  pin  bushing,  and  some  other  close  parts,  where  by  hand 
reaming  we  hold  a  limit  of  plus  or  minus  .00025. 

We  are  holding  today,  in  the  commercial  practice  of  the  shop, 
to  limits  which  but  a  few  years  ago  were  only  called  for  on  the  most 
accurate  tool  room  work.  However,  this  is  the  result  of  first  class 
inspection  methods  combined  with  properly  designed  jigs  and  fix- 
tures. 

Of  course  you  realize  that  in  the  manufacture  of  large  numbers 
of  interchangeable  parts,  speed  in  manufacturing  can  only  be  ob- 
tained through  close  limits  which  give  a  high  degree  of  interchange- 
ability.  Quality  can  be  controlled,  if  quality  is  the  idea  of  the 
Management;  if  the  people  behind  an  enterprise  have  a  genuine  de- 
sire to  get  quality  and  are  willing  to  pay  the  price,  it  should  be 
borne  in  mind  that  it  costs  money  initially  to  produce  quality,  to  get 
a  job  up  to  the  highest  standard  of  manufacture.  However,  once  that 
standard  is  reached  it  can  be  maintained  cheaper  than  it  is  possible 
to  maintain  a  lower  standard,  owing  to  the  fact  that  pieces  assemble 
with  greatly  increased  speed  when  fitting  in  an  Assembly  department 
is  entirely  eliminated. 

With  reference  to  the  crankshaft  and  the  camshaft,  we  check 
the  overall  and  intermediate  dimensions  in  a  fixture  gage  which  has 
stops  at  different  points,  allowing  the  use  of  a  "go"  and  "no  go" 
feeler.  Inspection  by  this  method  is  quicker  and  more  accurate. 
We  find  that  the  twin-six  crankshaft  supported  only  on  the  front  and 
rear  bearing  will  not  sag  anything  over  night,  but  in  a  test  covering 
a  week's  duration  we  found  a  sag  of  .0005. 


THE  PRECISE  CONTROL  OF  PROCESSES  333 

It  might  be  of  interest  to  you  to  know  that  our  Liberty  Engine 
crankshaft  supported  on  the  front  and  rear  bearing  would  sag  over 
night  from  .001  to  .0015  while  the  sag  in  a  week  would  be  .003. 
Of  course,  this  was  due  to  the  extremely  long  shaft  and  a  fair  degree 
of  flexibili  ty .  However,  I  do  not  think  that  any  close  comparison  can 
be  drawn  as  to  the  sag  of  a  crankshaft,  because  so  many  items  enter 
into  the  consideration,  such  as:  design,  material,  heat  treatment 
of  the  material,  manner  in  which  it  is  processed,  the  amount  of 
straightening  that  is  done,  room  temperatures,  and  consequently  tests 
of  this  kind  may  be  only  considered  comparatively.  Of  course, 
comparisons  will  be  useful  provided  they  are  made  on  shafts  of  simi- 
lar design.  This  question,  however,  reaches  into  technical  details 
which  are  beyond  consideration  of  ordinary  inspection  practice. 

The  tolerances  disclosed  in  these  cases  are  typical  and 
indicate  the  precision  obtained  in  daily  manufacturing  in 
those  motor  car  factories  where  dimensional  control  has  been 
carried  to  the  highest  practicable  standard  of  achievement. 
Works  of  this  sort  employ  from  20,000  to  40,000  limit  gages, 
whose  cost  runs  into  the  hundreds  of  thousands  of  dollars. 
The  inspection  of  finished  parts  alone  may  require  72  hours 
per  car.  Some  other  industries  apply  more  gages,  occasion- 
ally as  many  as  50,000  in  one  factory;  but  few,  if  any, 
achieve  the  precision  of  the  automobile  factories,  on  a 
quantity  production  basis — day  in  and  day  out.  With  over 
10,000,000  motor  vehicles  in  the  country,  everyone  has  a 
chance  to  familiarize  himself  with  their  various  parts. 
Consequently,  the  precision  for  principal  dimensions  gives 
a  pretty  good  general  idea  of  commercial  possibilities  for 
various  sorts  of  machine  work. 

Tables  of  Tolerances 

Another  source  of  information  as  to  precision  is  to  be 
found  in  tables  of  tolerances.  In  a  sketch  furnished  by  the 
C.  E.  Johansson  Company,  Inc.  (see  Figure  80),  various 
kinds  of  fits  are  shown,  together  with  two  tables  of  tolerances 


334 


THE  CONTROL  OF  QUALITY 


Illustrating  the  Different  C/asses  of 
F/ts  Repaired  in  the  Construction 
of  a  Simple  Drill  Press  . 


L  iyht  Rurinlny  Tit 


>^ 

-^3,.    r 

_  i.  -^^H  Running  fit 


-    Sliding  fit 


force  Tit 


Figure  80.     Sketch  of  Drill  Showing  Various  Fits — Johansson 


THE  PRECISE  CONTROL  OF  PROCESSES 


335 


and  limits  (Figures  81,  82,  83,  and  84).  One  set  of  data  is 
based  upon  the  hole  system,  in  which  the  hole  is  taken -as 
the  reference  point  of  greatest  accuracy,  and  the  other  is 
based  upon  the  shaft  system.  Since  the  recent  develop- 
ments in  greater  precision  of  work,  especially  as  regards 
grinding,  there  would  seem  to  be  little  need  of  considering 


DIAGRAM  OF 

LIMIT  SYSTEM 

SHAFT— BASIS 


TOLERANCES:  THE  SHAFT  -  1OO: 


Figure  81.     Diagram  of  Limit  System — Shaft  Basis — Johansson 

whether  we  should  work  from  the  hole  or  the  shaft,  but  the 
figures  are  interesting  as  a  guide  nevertheless. 
k-i  In  recent  years  considerable  pioneer  work  has  been  done 
in  England  toward  assembling  useful  data  on  precision  and 
pioneer  work  of  the  same  sort  has  started  in  this  country. 
In  July,  1920,  Mechanical  Engineering  announced  the  forma- 
tion of  a  sectional  committee  of  the  American  Society  of 
Mechanical  Engineers  for  the  purpose  of  studying  and  re- 
porting on  plain  limit  gage  standards  and  machined  fits. 


336 


THE  CONTROL  OF  QUALITY 


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THE  PRECISE  CONTROL  OF  PROCESSES 


337 


The  questionnaire  prepared- by  the  committee,  as  published 
in  Mechanical  Engineering  for  February,  1921,  states  that 
the  practice  of  one  well-known  firm  is  as  follows  for  various 
classes  of  fits : 

CLASS  No.  i     LOOSE  FITS 
Machined  fits  of  agricultural,  domestic,  and  other  machinery 

of  similar  grade  (wagons  excepted) 
Mining  machinery 

Controlling  apparatus  for  marine  work,  etc. 
Textile  and  rubber  machinery,  candy  and  bread  machinery, 

and  others  of  similar  grade 
Some  parts  of  ordnance 
General  machinery  for  manufacturing. 

CLASS  No.  2     MEDIUM  FITS  (MOVING  PARTS) 
2a  High  Speeds  (over  600  r.  p.  m.)  and  Heavy  Pressures 
Electrical  machinery 
High-speed  parts  of  woodworking  machines 


C.  E.  JOHANSSON 


DIAGRAM  OF 

LIMIT  SYSTEM 

HOLE-BASIS 


TOLERANCES:  THE  HOLE  -  1OOs 


Figure  83.     Diagram  of  Limit  System — Hole  Basis — Johansson 
22 


338 


THE  CONTROL  OF  QUALITY 


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THE  PRECISE  CONTROL  OF  PROCESSES  339 

Sewing  machines 
Machine    tools 
Locomotives 
Printing  machinery 
Automotive 
Ordnance 

General  machinery  for  manufacturing. 
A  well-known  firm  uses  allowances  of  0.0005-0.004  in.  up  to  6 
in.  for  work  of  this  class. 

CLASS  No.  2     MEDIUM  FITS 
2h  Ordinary  Speeds  (under  600  r.  p.  m.)  and  Light  Pressures 

Machine  tools 

Printing  presses  and  machinery 

Typewriters,  calculating  machines,  etc. 

Locomotives 

Automotive — general  parts 

Textiles,  rubber  machinery 

Ordnance 

General  machinery  for  manufacturing. 

A  well-known  firm  uses  allowance  of  0.0005-0.0025  in.  up  to  6 
in.  for  work  of  this  class. 

CLASS  No.  3    SNUG  FITS 

(Designated  as  the  closest  fit  that  can  be  assembled  by  hand.) 
3a  Slight  Allowance  (0.00025  to  0.00075  in.) 

Gear  trains  and  change  gears  for  general  work 

Mating  parts,  fixed  or  not,  moving  on  each  other,  such  as 

studs  for  gears  and  levers,  keys 
General  machinery  for  manufacturing. 

3b  Close  Fit  (commonly  known  as  wringing  fit,  no  allowance, 
not  considered  interchangeable  manufacturing  but  selec- 
tive assembling) 
Crankshafts 

Precision-ground  machine  spindles 
Gears  in  index  train  of  precision  gear-cutting  machines 
Slots  and  tongues  such  as  are  used  for  grinding  machines, 

milling  machines,  etc. 

Surveying  and  scientific  dental  instruments,  etc. 
General  machines  for  manufacturing. 


340  THE  CONTROL  OF  QUALITY 

CLASS  No.  4     TIGHT  FITS 
4a   Drive  Fits  for  Light  Sections 
Automotive 
Ordnance 

General  machines  for  manufacturing. 

A  well-known  firm  uses  negative  allowance  from  0.00025  to 
o.ooi  in.  up  to  6  in. 

4!)  Force  Fits  for  Heavy  Sections 
Locomotive  and  car  wheels 
Crank  disks,  armatures,  flywheels 
Automotive 
Ordnance 

General  machines  for  manufacturing. 

A  well-known  firm  uses  negative  allowance  from  0.00075  to 
0.005  m-  UP  to  6  in. 
4c  Shrink  Fits 

Locomotive  tires  and  similar  work 
Ordnance. 

A  well-known  concern's  practice  is  as  follows :  Where  thickness 
exceeds  3/8  in.,  0.0005  to  0.005  m-  UP  to  6  in.  in  diameter.  Where 
thickness  is  less  than  3/8  in.,  up  to  6  in.  in  diameter,  0.00025  in.  to 
0.0015  i'n. 

It  is  to  be  hoped  that  this  committee  will  cover  the  field 
of  practicable  precision  of  machining  processes  in  consider- 
able detail,  and  that  this  data  will  be  kept  up  to  date  for 
the  guidance  of  industry. 

Precautions  for  Obtaining  Precise  Work 

Among  the  general  considerations  to  which  attention 
should  be  given  in  bringing  processes  under  control,  one  of 
the  most  evident,  but  one  of  the  least  observed,  is  to  make 
the  tool  set-up  a  fool-proof  one.  There  is  so  much  need  of 
all  available  time,  care,  and  attention  to  details  in  close 
work  that  everything  which  can  be  done  to  free  the  operator 
from  unnecessary  strain  in  these  particulars  should  be  done. 
Not  once  but  several  times  during  the  last  years,  the  writer 


THE  PRECISE  CONTROL  OF  PROCESSES  341 

has  heard  superintendents  or  engineers  say  something  like 
this: 

We  can't  seem  to  get  results  in  the  ....  shop,  and  it  is  due  to 
nothing  but  the  foremen's  failure  to  handle  their  men  so  as  to  get  the 
answer.  I  know  that  the  tools  and  gages  are  O.K.,  because  I  have 
made  the  complete  part  myself.  Only  yesterday  I  carried  a  piece 
through  each  operation  personally  and  it  came  to  the  gages  in  fine 
shape.  That  proves  everything  is  all  right  except  that  the  shop 
executives  don't  exercise  proper  control  over  production. 

As  a  matter  of  fact  it  proves  nothing  of  the  sort.  All 
it  does  prove  is  that  a  skilful  mechanic  with  years  of  experi- 
ence can  make  a  good  part  with  the  facilities  provided. 
We  knew  that  already.  It  has  been  done  before. 

Having  detected  the  fallacy  in  the  above  remark,  let  us 
consider  some  of  the  things  that  such  a  test  does  not  prove. 
In  the  first  place,  such  a  test  does  not  show  that  unskilled 
operators  can  produce  good  work  with  the  available  equip- 
ment, nor  does  it  prove  that  they  will  do  so,  especially  if  the 
wage  system  is  such  as  to  create  a  strong  incentive  for  quan- 
tity of  individual  output.  Most  large-scale  enterprises  are 
conducted  in  a  way  to  place  a  heavy  emphasis  on  quantity  of 
output.  Nor  does  it  indicate  that  the  gages  will  be  applied 
correctly  by  unskilled  inspectors,  nor  that  the  available 
machine-setters  and  adjusters  are  trained  to  their  work,  nor 
that  the  shop  arrangements  and  system  are  suitable  for  the 
general  conditions  as  they  exist  in  fact.  In  short,  we  are 
faced  with  a  condition  and  not  a  theory.  The  solution  lies 
in  shaping  everything  to  the  actual  environment.  We  must 
deal  with  things  as  they  are,  not  as  they  used  to  be,  or  as 
they  might  be  under  different  circumstances. 

There  is  a  way  to  meet  the  situation.  When  a  task  calls 
for  greater  skill  than  the  available  labor  possesses,  split  the 
task  into  simple  operations,  any  one  of  which  will  be  within 
the  capacity  of  such  labor.  This  is  the  old,  well-known, 


342  THE  CONTROL  OF  QUALITY 

thoroughly  tested,  but  little  appreciated,  cure  for  the  con- 
dition— namely,  a  judicious  application  of  division  of  labor. 
Similarly  the  principle  of  analyzing  everything  into  simpler 
parts  must  be  used  to  the  end  that  each  man's  work  will  be 
well  within  his  capacity,  for  it  is  through  these  men  that  the 
result  will  be  achieved,  and  only  through  them.  This  simpli- 
fying process  must  be  used  in  every  element  of  the  project- 
tools,  gages,  shop  arrangement,  shop  systems,  and  organiza- 
tion. This  much  is  axiomatic;  nor  should  it  be  forgotten 
that  such  a  differentiation  greatly  complicates  the  problem 
of  co-ordinating  the  different  constituent  parts  of  the  work. 

In  the  second  place,  the  tool  and  gage  designers  can 
help  safeguard  standards  by  eliminating  process  hand-work 
as  much  as  possible,  and  by  simplifying  the  tool  and  gage 
designs  in  so  far  as  is  practicable.  Tool  equipment  should 
be  simple  and  much  more  rugged  than  heretofore.  Forcing 
light  work  should  be  made  difficult.  The  factor  of  careless 
machine  operation  should  be  discounted  by  skilful  designing 
for  chip  clearances  and  bedding  points,  because  careful  plac- 
ing of  work  cannot  be  counted  upon.  The  same  line  of 
thought  applies  to  gages — the  complicated  gage  with  sev- 
eral gaging  points,  flush  pins,  etc.,  should  give  way  to  single 
measurement  limit  gages.  Adjustable  limit  gages  can  be 
used  to  great  advantage.  In  some  cases  working  gages 
should  have  closer  limits  than  salvage  gages,  but  this  is  a 
practice  that  must  be  settled  with  reference  to  individual 
problems.  Templates  of  form,  outline,  or  profile  should  be 
preserved  systematically  and  checked  methodically  for  both 
cutters  and  gages.  In  this  checking  there  should  be  em- 
ployed the  most  sensitive  tactile  skill  obtainable. 

In  the  endeavor  to  make  things  fool-proof — a  process 
in  which  nothing  must  be  taken  for  granted  and  every  detail 
carefully  considered  because  the  effect  of  such  details  is 
multiplied  enormously  through  repetition,  so  that  little 


THE  PRECISE  CONTROL  OF  PROCESSES  343 

things  determine  results — there  is  usually  no  occasion  for 
continuing  to  worry  about  such  matters  as  keeping  the 
bedding  points  free  from  chips.  A  little  care  in  the  design 
of  the  tool  will  permit  chips  to  fall  away  from  the  work  in- 
stead of  onto  the  bedding  surfaces.  Very  often  an  auxiliary 
device  may  be  provided  for  blowing  the  chips  away  auto- 
matically. 

The  work  itself,  as  well  as  the  tool,  should  be  designed 
so  as  to  reduce  the  chance  of  error  from  forcing  a  tool  and 
so  as  to  permit  accurate  holding  of  the  work  when  it  is  pre- 
sented to  the  tool.  It  is  good  practice  when  possible  to 
work  from  holes  as  locating  points  for  a  series  of  operations. 
The  objection  to  this  practice  for  many  operations  lies  in 
the  fact  that  the  work  is  soft  for  machining,  and  the  holes 
wear.  A  little  ingenuity  will  avoid  this  trouble.  Very 
frequently  a  false  hole  or  slot  may  be  created  in  the  place 
where  the  metal  will  be  cut  away  later.  When  this  cannot 
be  done,  there  seems  no  reason  why  holding  lugs  cannot  be 
added  to  the  part,  hollow-milled  in  a  jig,  used  for  bedding 
points  throughout  the  machining,  and  finally  cut  off.  In 
fact,  there  are  cases  where  this  has  been  done. 

The  Principle  of  Balance 

For  very  careful  and  accurate  control  of  a  process  used 
in  creating  a  uniform  product,  a  nice  balance  should  be 
provided,  as  a  direct  and  practicable  application  of  Newton's 
third  law  of  motion — "action  and  reaction  are  equal  and 
opposite."  Now  in  a  machine  tool  the  whole  supporting 
structure  which  presents  the  work  to  the  tool  should  provide 
a  wall  against  which  to  build  up  the  pressure  imposed 
by  the  tool  itself.  In  laying  out  the  equipment  for  any  proc- 
ess this  principle  should  be  carefully  considered  if  a  nicely 
balanced  application  of  force  must  be  made.  The  same 
idea  is  applicable  in  many  other  processes  where  irregular 


344  THE  CONTROL  OF  QUALITY 

or  jerky  action  may  be  avoided  by  balancing  the  opposing 
forces. 

When  difficulties  are  encountered  in  bringing  processes 
under  uniform  control,  one  good  way  of  deciding  whether 
the  method  is  correct  is  to  carry  it  to  the  extreme  in  the 
opposite  direction.  Thus,  Professor  John  E.  Sweet  states: 

To  demonstrate  that  this  is  right,  a  good  way  in  this,  as  in  most 
mechanical  problems,  is  to  carry  the  wrong  way  to  an  extreme  and 
note  the  consequences,  and  it  will  be  found  that  the  right  way  has 
already  been  carried  to  the  extreme  in  the  right  direction. 

The  Effect  of  Finish  on  Accuracy 

One  of  the  most  important  points  to  be  observed  in  in- 
structing machine  operators  is  care  of  the  work.  Attention 
to  quality  brings  about  the  creation  of  finer  work  and  that 
of  itself  usually  demands  respect ;  nevertheless  our  factories 
are  full  of  workmen  who  would  treat  bricks  with  much  more 
respect  than  they  do  steel  parts — bricks  would  break  if  they 
were  thrown  around,  whereas  steel  parts  only  become 
dented.  But  dents  and  scratches  require  more  polishing, 
more  grinding,  and  uniformity  of  dimension  is  lost.  On  the 
machine  itself  one  way  to  insure  greater  uniformity  is  to 
remove  vibration,  but  this  is  merely  another  application  of 
the  principle  of  balance  referred  to  above.  To  meet  the 
same  condition,  it  is  probable  that  finishing  operations, 
such  as  automatic  polishing  and  tumbling,  will  see  wider 
application  and  greater  refinement  in  the  future  because  of 
their  marked  advantages. 

Quick  Checks  on  Precision 

It  will  be  found  useful,  from  time  to  time,  to  apply  the 
method  of  taking  check  "borings"  in  the  factory,  in  order 
to  develop  additional  information  as  to  what  requires  cor- 
rection for  greater  uniformity.  It  is  suggested,  for  example, 


THE  PRECISE  CONTROL  OF  PROCESSES  345 

that  some  important  part  be  independently  checked  and 
measured,  beginning  with  the  tools  and  gages  and  conclud- 
ing with  the  measurement  of  the  parts  themselves,  proceeding 
from  operation  to  operation  straight  through  to  the  com- 
pletely assembled  mechanism.  There  are  other  quick  tests 
which  may  be  applied.  For  example,  a  check  on  the  uni- 
formity of  heat  treatment  may  be  obtained  by  supporting 
like  parts  in  like  positions  for  the  same  length  of  time  and 
measuring  their  sag.  It  was  in  connection  with  getting 
data  for  such  a  test  to  check  up  the  work  of  a  certain  factory 
that  the  information  relative  to  sag  of  crank-shafts  (referred 
to  on  pages  332  and  333  of  this  chapter)  was  obtained. 
The  work  as  performed  in  the  Packard  shops  was  taken  as 
standard  in  comparing  work  in  a  somewhat  similar  shop  do- 
ing cruder  work  and  located  many  hundreds  of  miles  away. 
The  results  were  very  interesting  indeed,  because  of  their 
divergence  and  lack  of  uniformity. 


CHAPTER  XXI 
THE  CONTROL  OF  COLOR1 

Application  of  Measurement  to  Other  Qualities 

Up  to  this  point  we  have  dealt  with  dimension  as  ex- 
emplifying cases  where  excellent  means  of  measurement 
exist.  Very  often  in  such  work  special  tool  equipment  is 
provided  which  works  from  a  pattern  made  with  the 
greatest  care,  the  tools  almost  automatically  following  this 
pattern  over  and  over.  Even  in  the  case  of  straight  ma- 
chine work  without  special  tools,  a  high  degree  of  precision 
is  possible.  Many  other  processes,  however,  have  not  yet 
been  regulated  with  such  precision.  Bringing  them  under 
uniform  control  involves  the  process  outlined  in  Chapter 
XIII,  "Measurement  and  Errors,"  but  before  we  are  in  a 
position  to  tabulate  the  various  errors  in  the  work  produced 
by  such  operations  or  processes,  it  is  necessary  to  develop 
some  systematic  method  of  recording  both  the  kinds  of 
errors  and  their  relative  occurrence  both  as  to  frequency 
and  size.  Color  is  a  typical  instance  of  this  general  class  of 
work— a  class  which  is  extremely  large  in  industry  today, 
but  which  will  be  gradually  reduced  and  brought  under 
control  as  time  goes  on  and  the  fight  continues  for  greater 
production  of  better  and  more  uniform  qualities  at  a  lower 
expenditure  of  effort. 

In  discussing  the  subject  of  measurement  in  Chapter 
XIII,  it  was  shown  that  the  control  of  any  quality  depends 
upon  measurement  as  a  starting  point,  and  that  measure- 
ment itself  is  a  process  beginning  with  the  selection  of  an 

1  For  an  authoritative  and  most  interesting  treatise  on  the  subject  of  color,  the  reader  is 
referred  to  "Color  and  Its  Applications,"  by  M.  Luckiesh,  Director  of  Applied  Science,  Nela 
Research  Laboratories  of  the  National  Lamp  Works,  General  Electric  Company. 

346 


THE  CONTROL  OF  COLOR  347 

arbitrarily  chosen  sample  which  is  suitable  as  a  standard  of 
comparison  for  the  quality  under  consideration.  The  next 
stage  consists  in  developing  a  scale  of  values  to  permit 
measures  of  the  quality  to  be  stated  in  figures,  and  the  final 
step  is  the  development  of  impersonal  measuring  instru- 
ments. Dimension  and  weight,  for  example,  have  reached 
the  last  stage  and  very  precise  instrumental  means  are 
available  for  control  purposes.  Many  other  qualities, 
however,  have  barely  reached  the  first  stage  of  control  by 
direct  comparison  with  standard  samples. 

Appearance  and  Color 

Of  the  several  qualities  that  define  the  character  of  the 
factory  product,  certainly  appearance  is  not  the  least  im- 
portant, and  throughout  a  wide  range  of  industries  color  is 
one  of  the  important,  if  not  the  most  important,  quality 
which  goes  to  make  up  appearance.  Frequently,  as  in  the 
case  of  chemicals  and  food  products,  color  is  an  indication 
of  other  qualities  in  addition  to  appearance.  Just  how 
valuable  a  uniformly  good  color  is  as  a  commercial  asset 
must  be  decided  in  the  light  of  the  special  business  situation. 
If  color  is  worth  controlling  to  a  commercially  uniform 
standard,  then,  as  in  the  case  of  the  qualities  of  dimension 
and  form,  we  must  define  the  standard  which  is  to  be  fol- 
lowed, adopt  processes  for  its  creation  that  are  uniformly 
controllable  within  the  limits  set,  and  provide  a  means  of 
comparing  the  results  by  some  suitable  method  of  measuring. 

Now  measurement,  as  we  have  seen,  is  the  proper  start-, 
ing  point,  and  this  involves  the  selection  of  a  standard  for 
comparison.  If  the  standard  is  one  which  permits  com- 
parisons in  figures,  like  the  standard  of  length,  so  much  the 
better.  Then,  instead  of  saying  that  an  article  is  ' 'slightly 
red"  or  a  "little  too  green,"  we  should  be  able  to  say  how 
red  it  is,  or  how  much  too  green.  In  that  event  we  might 


348  THE  CONTROL  OF  QUALITY 

hope  to  do  with  color  what  we  have  already  accomplished 
with  dimension,  by  working  out  the  relationship  between 
cause  and  effect.  When  it  became  possible  to  measure  in 
ten- thousandths  of  an  inch,  we  were  presently  in  a  position 
to  work  to  that  degree  of  accuracy — but  not  until  then. 
Hence,  in  the  case  of  color,  the  first  step  is  to  search  for  a 
proper  basis  of  establishing  such  a  standard  of  measurement. 

Standard  Samples 

The  simplest  scheme  would  be  to  select  a  series  of  samples 
of  the  goods  and  grade  them  according  to  an  arbitrary  scale 
with  reference  to  their  appearance.  Thus,  ten  samples  ar- 
ranged in  a  scale,  in  which  each  one  differed  from  its  neigh- 
bors by  an  equal  amount  of  color,  or  luster,  or  smoothness, 
would  provide  us  for  comparative  purposes  with  a  scale  of 
ten.  Sometimes,  a  simple  scheme  such  as  this  is  all  that  con- 
ditions warrant,  or  perhaps  it  may  be  the  best  we  can  do; 
but  it  is  entirely  too  coarse  for  precise  and  careful  work. 
The  lack  of  quantitative  comparison  greatly  hampers  any 
systematic  attempt  to  evaluate  deviations  from  standard 
and  therefore  to  develop  means  for  correcting  such  errors. 

The  Standard  Color  Card 

The  first  movement  in  our  industries  for  standardizing 
color  for  commercial  purposes  was  made  by  The  Textile 
Color  Card  Association  of  the  United  States,  in  developing 
a  series  of  color  cards  which  find  wide  use  in  most  of  the  in- 
dustries engaged  in  the  manufacture  of  clothing  and  the 
basic  materials  of  clothing.  The  fact  that  the  paint,  paper, 
and  some  other  industries  are  making  use  of  these  color 
cards  indicates  their  great  practical  value  in  reducing  losses 
of  various  sorts.  A  numbering  system  is  used  in  accordance 
with  the  following  scale,  standard  colors  being  indicated 
by  the  letter  6"  used  as  a  prefix : 


THE  CONTROL  OF  COLOR  349 

1st,  2nd,  3rd  figures  indicate  the  rela-     4th  figure  indicates  the  strength  of  the 
tive   proportion   of  the  component         color  designated  by  the  first  three 

parts  of  a  color :  figures : 

1  White  i  Lightest 

2  Red  2  Second  lightest 

3  Orange  3  Light 

4  Yellow  4  Medium  light 

5  Green  5  Medium 

6  Blue  6  Medium  dark 

7  Violet  7  Dark 

8  Gray  8  Second  darkest 

9  Black  9  Darkest 
o     No  change 

To  illustrate:     Turquoise  is  "S.  6153" 

6i53 
BLUE  WHITE  GREEN  LIGHT 

Principal  Principal  Secondary  Strength 

Color  Blend  Blend 

The  establishment  of  this  systematic  classification  of 
colors  for  commercial  purposes  in  the  textile  and  allied 
industries  is  evidence  of  a  highly  commendable  and  far- 
sighted  attitude  toward  solving  the  problem  of  color  con- 
trol. It  will  be  noted,  however,  that  in  its  last  analysis 
any  such  classification  depends  upon  the  integrity  of  the 
standard  samples  supplied  by  the  color  cards  themselves; 
the  samples  on  the  various  cards  must  be  alike  for  a  given 
color,  and  each  sample  should  be  as  little  likely  as  possible 
to  change  as  time  goes  on.  The  necessity  for  such  assump- 
tions can  only  be  offset  when  the  art  has  been  advanced  to 
a  point  where  construction  formulas  for  the  reproduction  of 
standard  colors  can  be  stated  in  terms  of  the  exact  propor- 
tions of  the  color-creating  factors,  and  the  colors  them- 
selves can  be  stated  in  impersonal  figures. 

A  similar  practical  contribution  towards  color  standard- 
ization was  made  by  the  late  A.  H.  Munsell  in  the  form  of  a 
color  notation  and  an  atlas  of  colors.2  The  atlas  consists 

2  A.  H.  Munsell,  "A  Color  Notation";  "The  Atlas  of  the  Munsell  Color  System." 


350  THE  CONTROL  OF  QUALITY 

of  a  series  of  charts  in  which  colored  samples  are  arranged  in 
accordance  with  the  Mimsell  color  system.  A  scientific 
investigation  of  this  system  was  undertaken  by  the  Bureau 
of  Standards  and  a  very  interesting  report  of  it  is  published 
under  the  title  of  "An  Examination  of  the  Munsell  Color 
System."3 

Dangers  of  Standard  Samples 

The  great  trouble  with  standard  samples  is  that  we  have 
no  assurance  that  they  are  not  continuously  changing. 
On  the  contrary,  we  can  be  sure  that  they  do  change,  and 
by  such  insidiously  small  increments  that  the  changes  are 
hard  to  detect.  The  sample  is  one  thing  today  and  some- 
thing else  almost  before  we  know  it.  More  dangerous  yet, 
we  may  not  know  that  its  appearance  has  altered.  In 
many  plants,  where  this  is  fully  appreciated  master  stand- 
ards are  kept.  When  it  is  the  custom  of  the  color  expert 
to  carry  in  his  mind  and  to  allow  for  any  slight  difference 
between  the  working  and  the  master  sample,  the  practice 
usually  leads  to  interesting  results. 

Just  as  in  the  case  of  dimension,  precise  control  of  color 
requires  a  more  absolute  method  of  measurement.  But  to 
fix  upon  that,  we  must  first  get  some  idea  of  what  makes 
color.  Perhaps  this  would  be  expressed  better  by  saying 
that  our  first  problem  is  to  determine,  as  nearly  as  we  can, 
what  color  is. 

What  Is  Color? 

If  a  truism  may  be  pardoned,  color  (and  for  that  matter 
any  quality  which  goes  to  make  up  appearance)  is  some- 
thing which  you  see  with  your  eyes.  What  else  can  it  be? 
And  the  eye  is  sensitive  only  to  light.  It  makes  no  differ- 


3  Bureau  of  Standards,  "Technologic  Paper  No.  167,"  by  Irwin  G.  Priest,  K.  S.  Gibson,  and 
H.  J.  McNicholas. 


THE  CONTROL  OF  COLOR  351 

ence  whether  the  particular  kind  of  appearance  we  are  deal- 
ing with  is  caused  by  a  mechanical  treatment  of  the  surface 
of  the  article,  or  by  stains,  pigments,  or  dyes,  or  whether 
the  subjective  sensation  of  color  is  due  to  some  inherent 
property  of  the  raw  material  from  which  the  article  is 
made.  But  irrespective  of  the  cause  of  color,  the  effect  is 
light,  so  that  as  a  starting  point  the  use  of  optical  methods 
is  indicated  at  once  as  the  only  sure  way  of  attacking  the 
problem,  both  for  standardizing  the  final  result  and  for 
measuring  the  effects  as  a  step  toward  controlling  the  agents 
used  to  create  that  result.  Thus,  color  considered  as  the 
final  effect  must  be  reduced  to  a  measured  basis  for  com- 
parison with  a  view  to  studying  the  causes  of  errors  or 
differences,  as  well  as  the  means  for  modifying  errors  and 
making  the  results  more  uniform. 

In  approaching  the  subject,  then,  from  the  standpoint 
of  color  considered  as  light,  it  should  be  observed  that  three 
principal  factors  are  involved,  since  without  any  one  of 
these  three  there  will  be  no  color — first,  the  illuminant,  or 
source  of  light,  which  may  be  regarded  as  the  effector; 
second,  the  subject,  or  the  thing  which  is  said  to  have 
color;  third,  the  eye  of  the  observer,  which,  as  the  receptor 
of  the  sensation,  is  merely  a  lenticular  instrument  adjust- 
able within  limits  but  varying  from  individual  to  individual 
and  from  time  to  time  even  for  the  same  individual.  Let  us 
now  consider  each  of  these  subjects  separately. 

The  Illuminant 

The  sensation  of  light  is  now  generally  considered  to  be 
caused  by  a  form  of  radiant  energy  which  occurs  in  a  va- 
riety of  wave  lengths  and  frequencies  of  vibration,  but 
which  passes  through  empty  space  without  appreciable 
change  in  velocity.  The  nervous  system  of  the  eye  is 
sensitive  to  this  radiant  energy  only  within  a  comparatively 


352 


THE  CONTROL  OF  QUALITY 


narrow  range,  as  indicated  in  Figure  85. 4  Beyond  this 
range,  in  one  direction,  are  found  the  ultra-violet  rays, 
whose  presence  is  made  known  by  their  chemical  or  actinic 
properties.  In  the  other  direction  are  the  infra-red  rays, 
which  are  noticeable  on  account  of  their  heating  effect. 
It  will  be  noted  also  from  the  relative  visibility  curve 


1.0U 


1.00 


0.90 

/ 

5 

0.90 

0.80 

/ 

\ 

0.80 

0.70 

i 

\ 

0.70 

0.60 

1 

\ 

0.60 

0.50 

s/ 

\ 

0.50 

0.40 

/ 

\ 

0.40 

0.30 

I 

\ 

0.30 

0.20 

h 

V 

0.20 

0.10 

A 

\ 

0.10 

0.00 

—  — 

' 



\ 

^= 

• 

0.00 

420 
Ultra-Violet  Violet  Blue 


500 


540  580          620 

Green    Yellow  Orange. 


G60 


700 
Red 


740          780 
Infra- Red 


Figure  85. 


Chart  for  Spectral  Analysis  of  Color  Showing  Relative  Visibility 
Curve 


(Figure  85)  that  the  eye  is  not  equally  sensitive  to  all  the 
visible  rays,  but  that  these  rays  begin  to  become  visible  at 
the  edge  of  the  ultra-violet  region,  reach  a  maximum  effect 
in  the  greens  and  yellows,  and  then  gradually  fade  away  and 
disappear  at  the  beginning  of  the  infra-red  region. 

Since  radiant  energy  is  transmitted  in  the  form  of 
waves,  and  since  each  wave  length  of  the  visible  rays  is 
associated  with  a  very  definite  color  sensation,  we  have  a 


4  This  follows  the  chart  used  by  the  Bureau  of  Standards  in  the  Munsell  color  examina- 
tion already  referred  to. 


THE  CONTROL  OF  COLOR  353 

convenient  way  of  exactly  indicating  any  particular  hue 
due  to  a  given  wave  length,  or  a  small  group  of  similar 
wave  lengths,  by  stating  that  wave  length  in  figures.  This 
is  especially  useful  since  the  eye  itself  is  capable  of  a  very 
sensitive  differentiation  between  the  various  wave  lengths. 
The  lower  scale  of  Figure  85  shows  the  wave  lengths  as- 
sociated with  the  principal  colors.  The  figures  stated  for 
wave  lengths  are  in  millimicrons,  or  millionths  of  a  milli- 
meter (about  a  25-millionth  of  an  inch). 

White  light  is,  of  course,  a  mixture  of  all  these  rays  in 
more  or  less  definite  proportions,  depending  upon  the 
source  of  light.  For  practical  purposes  it  may  be  taken  as 
the  effect  on  the  eye  of  average  noon  daylight.  It  should 
be  noted  also  in  this  preliminary  summary  that  daylight 
itself  is  varying  all  the  time  and  from  place  to  place.  Con- 
sequently, it  is  usually  anything  else  but  pure  white  light. 
This  fact  must  be  remembered  in  connection  with  any 
careful  work  with  color  for  the  reason  that,  no  matter  what 
the  subject  is,  only  such  color  can  be  seen  as  has  correspond- 
ing colored  rays  in  the  source  of  the  illuminant.  Thus,  a  so- 
called  green  surface,  which  reflects  only  green  light,  if  illumi- 
nated by  a  red  light  will  appear  black,  because  no  light  is 
reflected.  Consequently,  the  importance  of  having  a  stand- 
ard illuminant  for  color  work  becomes  obvious,  and  as  it  is 
merely  common  sense  to  keep  all  of  our  work  in  consonance 
with  the  ordinary  conditions  with  which  we  are  acquainted, 
a  light  source  as  nearly  as  may  be  like  natural  north  sky 
daylight  is  generally  taken  as  most  suitable  for  color-match- 
ing and  study.  Such  lights  are  obtainable  commercially 
and  are  made  by  filtering  out  the  rays  which  are  in  excess  of 
those  contained  in  average  north  sky  daylight.  When  the 
light  is  reflected  for  instrumental  use,  it  is  the  usual  practice 
to  employ  a  white  magnesia  block  or  some  equivalent,  as 
the  standard  white  for  comparison. 

23 


354  THE  CONTROL  OF  QUALITY 

The  Subject 

In  studying  the  characteristics  which  cause  an  object  to 
have  color,  let  us  consider  the  limiting  cases  first.  A  per- 
fect mirror  would  reflect  practically  all  of  the  light  from  the 
illuminant  and  the  result  would  be  the  same  as  looking  at 
the  illuminant.  At  the  other  extreme,  a  perfectly  black 
surface  would  absorb  all  of  the  light  and  reflect  none.  If 
the  object,  on  the  other  hand,  reflected  only  a  portion  of  the 
incident  light  without  changing  the  relative  distribution  of 
the  constituent  light  rays,  the  color  of  the  object  would  not 
be  different  from  that  of  the  illuminant,  but  it  would  be  less 
bright.  Thus,  if  the  illuminant  were  a  white  light  the  object 
would  appear  gray.  We  have  now  defined  white  light  or 
white,  black  or  the  absence  of  light,  and  the  neutral  grays, 
as  intermediate  stages  between  the  two  extremes  of  white 
and  black. 

Suppose,  however,  the  subject  does  not  equally  reflect  all 
of  the  incident  rays,  but  that  it  absorbs  some  of  them  and 
reflects  the  remainder.  This  process  of  selective  absorption 
and  reflection  brings  about  an  unbalanced  distribution  of 
the  light  rays  as  compared  with  the  normal  distribution  in 
white  light,  with  the  result  that  some  one  group  of  rays 
becomes  dominant.  For  example,  if  a  red  predominates 
in  the  light  reflected  by  the  subject,  we  say  that  the  subject 
is  colored  red. 

If  the  subject  is  a  fluid,  essentially  the  same  process  of 
selection  takes  place,  except  that  in  this  case  certain  rays 
are  absorbed  and  others  transmitted  so  that  we  have  selec- 
tive absorption  and  transmission.  That  is  to  say,  the  words 
used  are  different,  but  the  ideas  are  identical. 

Color  is  caused  in  several  other  ways,  such  as  by  the 
interference  of  light  rays  (as  for  example,  by  a  drop  of  oil  on 
water) ,  or  by  dispersion  of  light  (with  a  prism) ,  or  as  in  the 
case  of  fluorescent  and  phosphorescent  substances,  or  by 


THE  CONTROL  OF  COLOR  355 

polarization,  to  mention  a  few  instances  of  color  phenomena. 
In  industrial  work,  however,  selective  absorption  is  by  far 
the  most  frequently  encountered. 

The  Eye 

For  our  present  purpose  the  eye  may  be  considered  as 
an  optical  instrument  of  lenticular  form  which  is  the  inter- 
mediary between  the  brain  and  the  external  causes  of  light 
and  color.  The  eye  views  a  group  of  colored  rays,  or  rays  of 
different  wave  lengths,  solely  as  an  intermingled  group  and 
sees  only  the  average  result  of  the  mixture,  e.g.,  white  light. 
In  this  sense  it  is  a  synthetic  instrument  incapable  of  ana- 
lyzing the  light  presented  to  it,  or  of  separating  out  the  in- 
dividual rays.  In  order  to  accomplish  such  analysis,  the 
eye  requires  the  assistance  of  an  instrumental  device  such 
as  the  prism,  or  the  ruled  grating,  or  a  color  filter,  as  will  be 
shown  presently.  Without  such  a  device  it  is  impossible  to 
view  the  constituent  colors  of  any  mixture  separately. 
Thus  when  one  mixes  a  blue  powder  with  a  yellow,  the  eye 
presently  sees  only  the  green  effect  of  the  combination. 

The  Color  Constants 

On  the  other  hand,  the  eye  can  analyze  color  with  ref- 
erence to  three  so-called  color  constants  known  under  vari- 
ous terms  as  set  forth  below.  Says  Dr.  M.  Luckiesh: 

One  of  the  greatest  needs  in  the  art  and  science  of  color  is 
a  standardization  of  the  terms  used  in  describing  the  quality  of 
colors  and  an  accurate  system  of  color  notation.  ...  The 
quality  of  any  color  can  be  accurately  described  by  determining 
its  hue,  saturation  or  purity,  and  its  brightness. 

Hue  (sometimes  called  "color  tone"  or  "quality")  is  the 
kind  of  color  with  reference  to  the  spectral  color  scale.  Thus 
a  color  whose  predominating  group  of  rays  are  in  the  red  is 
said  to  have  red  as  the  dominant  hue.  When  color  is 


356  THE  CONTROL  OF  QUALITY 

measured  instrumentally  the  dominant  hue  is  stated  in 
figures  as  the  wave  length  of  the  spectral  color  correspond- 
ing to  the  dominant  hue.  The  hues  of  the  non-spectral 
purples  are  handled  by  taking  the  dominant  hues  of  their 
complementary  5  colors. 

Purity  (also called  "saturation,"  "chroma,"  "strength," 
or  "intensity")  indicates  how  closely  the  constituent  rays 
approximate  to  none  but  rays  of  the  dominant  hue.  Spec- 
tral colors  are  pure,  but  other  colors  are  composed  of  many 
other  rays  than  those  which  predominate — hence  the  purer 
the  color,  the  nearer  it  is  in  composition  to  the  spectral  color 
of  corresponding  hue. 

In  instrumental  measurements  of  color,  since  any  color 
may  be  matched  by  diluting  a  given  spectral  color  with 
white  light,  the  relative  quantity  of  white  light  required  for 
the  match  is  used  as  the  measure  of  purity  and  is  expressed 
in  figures  as  a  percentage.  The  purity  becomes  greater 
as  the  percentage  of  white  light  required  for  a  match  be- 
comes less.  As  stated  under  "hue,"  purples  form  an  excep- 
tion, but  these  are  handled  by  working  in  terms  of  the  cor- 
responding complementary  colors. 

Brightness  (also  called  "luminosity,"  "value,"  or 
"tone")  relates  to  the  total  amount  of  light  reflected  or 
transmitted,  regardless  of  hue  or  purity — thus  a  neutral 
gray  photograph  of  colored  objects  shows  variations  in 
brightness  only.  It  is  measured  by  comparing  the  subject 
with  a  surface  of  known  brightness,  the  result  being  ex- 
pressed as  a  percentage  of  the  standard  of  brightness. 

The  ideas  conveyed  by  the  above  definitions  will  be  clar- 
ified by  referring  to  the  graphs  shown  in  Figure  86.  Curve 
a  is  a  gray  because  it  contains  equal  proportions  of  all  the 
special  colors  and  differs  from  white  only  in  reduced  bright- 
ness. Curves  b,  c,  and  d,  are  all  colors  of  red  hue,  of  which  d 

5  A  complementary  color  may  be  defined  by  stating  that  when  white  light  is  split  into  two 
parts  the  colors  thus  formed  are  complementary  to  each  other. 


THE  CONTROL  OF  COLOR 


357 


is  the  brightest,  since  it  reflects  the  most  light,  and  c  is  the 
purest  because  it  has  the  least  admixture  of  other  rays 
than  red  rays.  Curve  e  is  a  blue.  Differences  in  purity 
may  be  accentuated  by  plotting  the  curves  on  logarithmic 


paper. 


Tints  are  formed  by  diluting  a  color  with  white,  i.e.,  by 
reducing  the  purity;  e.g.,  spectral  colors  are  pure — pinks, 


i.oo 


1.00 


Figure  86.     Chart  for  Spectral  Analysis  of  Color  Showing  Typical  Color 
Analyses  Plotted  as  Curves 

which  are  tints  of  red,  are  not  found  in  the  spectrum.  Shades 
are  produced  by  admixing  black,  i.e.,  by  reducing  brightness 
without  affecting  hue  or  purity. 

The  above  facts  are  of  interest  in  the  practical  study  of 
color,  for  the  reason  that  it  would  seem  desirable  to  analyze 
and  measure  color  in  terms  of  the  dimensions,  such  as  hue, 
purity,  and  brightness,  which  the  eye  is  capable  of  seeing 
without  instrumental  assistance.  This  would  appear  to  be 
the  natural  way  to  approach  color  problems  instead  of 


358  THE  CONTROL  OF  QUALITY 

using  some  system  of  combining  primary  colors,  but  in 
either  case  practical  difficulties  must  be  overcome  in  any 
given  industrial  application. 

Color  Vision 

As  might  be  expected,  the  human  eye  is  quite  variable 
in  the  way  in  which  it  sees  color.  It  varies  from  time  to 
time  with  the  same  individual  and  very  seriously  from  in- 
dividual to  individual.  The  lack  of  a  definite  and  precise 
terminology  for  color  among  the  general  public  has  resulted 
in  a  looseness  of  usage  which  accentuates  this  source  of  per- 
sonal error.  Many  cases  of  so-called  color  blindness  have 
been  found  to  be  nothing  but  lack  of  education  of  the  eye. 

The  eye  of  a  highly  trained  color  expert  or  matcher  is 
extremely  sensitive  to  very  small  color  differences  and  dis- 
tinctions. This  fact  is,  in  the  writer's  opinion,  one  of  the  rea- 
sons why  color  in  the  arts  has  not  been  reduced  to  a  basis  of 
measurement  to  any  considerable  extent,  outside  of  the 
physics  laboratory.  The  chemistry  of  dyestuffs  and  pig- 
ments has  received  very  intensive  study,  because  for  their 
intelligent  application  such  study  has  been  absolutely  nec- 
essary; but  the  very  ability  to  perceive  small  differences  in 
the  color  effects  resulting  from  the  use  of  such  tinctorial 
agents  has  lead  to  ignoring  the  very  desirable  and  vitally 
important  features  of  measurement.  Thus,  in  the  factory 
one  hears  such  expressions  as  the  following:  "The  color  is 
a  little  too  much  on  the  red  "  — "  It  has  a  slight  red  cast " 
"  1 1  is  too  fine ' '—  '  Too  nice ' '— ' '  Too  quiet ' '— ' '  Not  enough 
depth" — and  so  on.  The  absence  of  any  means  for  quan- 
titative measurement,  or  the  failure  to  develop  and  utilize 
means  for  stating  in  figures  how  much  these  color  errors  are, 
has  stood  in  the  way  of  progress  toward  finding  out  the 
proper  adjustments  and  corrections  of  processes  so  that 
they  could  be  standardized. 


THE  CONTROL  OF  COLOR 


359 


Methods  of  Analyzing  Color 

Color  can  be  analyzed  for  purposes  of  study  in  much  the 
same  way  that  it  is  created,  if  use  is  made  of  various  devices 
which  break  up  light  into  its  constituent  parts.  Thus,  dif- 
fraction by  the  use  of  a  parallel-ruled  grating  is  one  means 
which  may  be  used,  but  the  best  known  device  is  a  simple 
prism  when  used  as  a  means  of  dispersion.  As  shown  in 
Figure  87,  light  rays  of  different  wave  lengths  bend  differ- 


Figure  87.     Sketch  of  Prism  and  Spectrum 

ently  in  passing  through  a  prism  of  glass  of  triangular  cross- 
section  and  thus  are  dispersed  in  a  systematic  way.  The 
consequence  is  that  the  rays  of  different  wave  length  are 
separated  so  that  viewing  a  ray  of  light  which  has  been 
dispersed  by  a  prism  shows  a  band  of  separate  colors  which 
is  known  as  the  ''spectrum." 

In  other  words,  each  color  in  the  spectrum'  is  a  small 
group  of  light  of  similar  wave  lengths  and  is  the  nearest  to  a 
truly  pure  color  to  be  found  in  nature.  It  is  for  this  reason 
that  purity,  as  denned  on  page  356,  is  expressed  as  a  per- 
centage, indicating  its  nearness  in  this  respect  to  the  spectral 
color  of  the  same  hue,  and  showing  its  degree  of  freedom 
from  all  other  colors  except  the  dominant  hue. 

The  use  of  a  simple  piece  of  glass  to  produce  a  spectrum 


360  THE  CONTROL  OF  QUALITY 

should  be  a  constant  reminder  that  the  world  is  not  only 
given  to  us  as  a  great  problem  to  solve,  but  also  that  the 
means  of  working  out  the  problem  are  at  hand  and  in  fact 
very  often  exist  in  very  simple  and  readily  accessible  form. 
Who  would  suspect  that  the  ordinary  white  light  of  a  gloomy 
day  contains  the  hidden  beauty  which  is  to  be  found  only  in 
the  pure  spectral  colors?  The  eye  cannot  see  them  with- 
out the  assistance  of  very  simple  means,  yet  it  was  not  until 
1666  that  Sir  Isaac  Newton  used  the  prism  to  create  a  rain- 
bow at  will. 

Analysis  by  Primary  Colors 

Color  may  be  analyzed  also  by  allowing  light  to  pass 
through  monochromatic  niters.  Viewing  a  subject  or, 
more  properly  speaking,  the  ray  of  light  from  the  subject 
through  a  filter  (of  stained  glass  or  gelatin)  which  allows 
only  green  to  pass,  will  give  a  very  good  idea  of  the  amount 
of  green  present.  Similarly,  the  use  of  other  color  filters  per- 
mits a  more  complete  analysis.  Further,  as  is  well  known, 
it  is  possible  to  match  any  hue  with  a  suitable  combination 
of  three  primary  colors.  There  are  two  or  three  things  to 
remember,  however,  when  speaking  of  primary  colors. 
First,  since  the  eye  is  an  averaging  instrument,  there  are 
several  combinations  of  three  colors  which  will  yield  the 
same  result  to  the  eye  although  upon  analysis  the  spectral 
composition  would  prove  to  be  quite  different  in  each  case. 
In  other  words,  the  same  effect  may  be  brought  about  by 
mixture  of  different  sets  of  carefully  selected  colors. 
Second,  colored  lights  may  be  mixed  by  addition  of  colored 
light  rays  and  each  addition  tends  toward  the  production  of 
white.  This  will  be  evident  from  a  consideration  of  the  fact 
that  white  light  itself  is  the  summation  of  all  the  colored 
rays.  The  "additive"  primaries  are  red,  green,  and  blue. 
Third,  color  as  ordinarily  produced  in  the  arts  is  the  result, 


THE  CONTROL  OF  COLOR  361 

on  the  other  hand,  of  the  successive  subtraction  of  light,  due 
to  the  fact  that  each  stain,  dyestuff,  or  pigment  selectively 
absorbs  some  of  the  incident  light.  Consequently,  as  Pat- 
erson6  says,  "every  admixture  of  colour  is  a  step  towards 
darkness."  The  " subtractive "  primary  colors  are  ordi- 
narily termed  red,  yellow,  and  blue.  Luckiesh  states,  how- 
ever, that  they  would  be  more  exactly  described  as  purple, 
yellow,  and  blue-green.  These  subtractive  primaries  are 
what  most  people  ordinarily  call  the  primary  colors.  As  a 
matter  of  fact,  they  are  only  primaries  for  color-mixing  of 
stains,  pigments,  and  dyes.  They  are,  moreover,  the  com- 
plementaries  of  the  additive  primaries  for  mixing  colored 
lights.7 

Instruments  for  Measuring  Color 

A  large  number  of  instruments  for  analyzing  and  meas- 
uring color  are  in  constant  use  in  the  physics  laboratory. 
These  instruments  are  based  on  various  adaptations  of  the 
principles  outlined  above.  Although  some  of  them  have 
been  employed  in  the  arts,  their  main  use  has  been  in  labora- 
tory work.  In  general,  they  have  not  been  used  to  any- 
thing like  the  extent  that  the  resultant  economies  to  be 
obtained  from  their  application  would  warrant.  This  is 
partly  owing,  as  already  stated,  to  the  failure  of  manufac- 
turers to  realize  the  vital  importance  of  measurement  in 
bringing  some  of  our  long-established  processes  under  more 
precise  technical  control,  and  partly  owing  to  the  fact  that 
some  of  the  instruments  require  modification  to  make  them 
more  suitable  for  general  industrial  use,  as  will  be  presently 
indicated. 

Basic  control  instruments  belong  to  the  spectrometer 
class.  Some  of  them  look  quite  complicated,  but  they  really 


6  See  David  Paterson,  "Textile  Colour  Mixing,"  p.  34. 

7  "Color  and  Its  Applications,"  by  M.  Luckiesh,  Chapter  III. 


362  THE  CONTROL  OF  QUALITY 

consist  of  a  simple  application  of  some  equally  simple  optical 
parts.  A  prism  (or  sometimes  a  grating)  is  used  to  break 
light  up  into  its  constituent  colored  rays,  lenses  mounted  in 
telescopes  are  used  to  magnify  the  image  of  the  spectrum 
thus  created  by  the  prism,  and  these  elements  of  the  instru- 
ment are  mounted  in  such  an  adjustable  relation  to  each 
other  that  a  scale  can  be  marked  off  on  the  instrument  to 
show  the  wave  length  of  each  color.  To  accomplish  the 
latter  purpose,  either  the  telescope  or  the  prism  is  revolved 
to  bring  each  spectral  color  into  the  viewing  axes,  and  the 
corresponding  wave  length  is  shown  on  a  calibrated  scale. 

The  Spectrophotometer 

The  Spectrophotometer  is  an  instrument  for  breaking  up 
light  from  the  subject  into  its  constituent  rays  (this  is  the 
spectroscopic  part  of  the  instrument)  and  for  measuring  the 
quantity  of  each  part  of  such  light  against,  or  as  a  percent- 
age of  the  same  rays  from  a  standard  white  light  (this  is 
the  photometric  part  of  the  instrument).  Obviously,  by 
reason  of  the  fact  that  it  measures  the  relative  quantity  of 
each  colored  ray  present  in  any  light,  the  Spectrophotometer 
is  the  basic  control  instrument  for  color.  As  shown  in  Figure 
88,  it  consists  of  two  spectroscopes  mounted  so  that  the 
intensity  of  rays  of  like  wave  length  in  the  two  spectra  can 
be  compared  by  placing  them  side  by  side  in  the  field  of 
view.  Light  is  taken  from  a  standard  source  6"  and  from 
the  subject  Si.  The  two  rays  enter  a  Lummer-Brodhun 
photometer  cube  so  arranged  that  after  being  dispersed  by 
the  prism  they  may  be  viewed  in  juxtaposition  through  the 
telescope.  It  is  thus  possible  to  select  one  spectral  color 
after  another  and  by  the  use  of  a  flicker  or  other  type  of 
photometer,  to  measure  the  quantity  of  said  color  as  a  per- 
centage of  a  standard  spectral  color. 

The  result  obtained  is  more  clearly  shown  by  reference 


THE  CONTROL  OF  COLOR 


363 


to  Figure  86,  in  which  the  curves  of  several  spectrophoto- 
metric  measurements  are  plotted. 

The  Monochromatic  Colorimeter 

As  has  been  seen,  the  spectrophotometer  gives  us  a  com- 
plete analysis  of  any  color,  and  when  the  results  are  plotted 
graphically  it  is  possible  to  get  a  very  fair  idea  of  the  domi- 
nant hue,  the  purity,  and  the  brightness.  To  measure 
hue,  purity,  and  brightness  of  a  color  in  terms  of  figures 
directly  and  without  computation  requires,  however,  one 
other  instrument,  which  may  be  regarded  as  the  second 
basic  control  instrument,  known  as  the  monochromatic 

# 

Sj- Light  from  Subject 


Photometer 
Cube  which 


results  in  a 
Field  of  View 
as  below. 


--- ^S-Standard  Light 


Eye  of  Observer 
Figure  88.     Diagram  of  Spectrophotometer 
(After  Luckiesh) 


364  THE  CONTROL  OF  QUALITY 

colorimeter,  of  which  the  Nutting  colorimeter  (made  by 
Adam  Hilger,  Ltd.,  London)  is  doubtless  the  latest  and  best 
known  type.  It  consists  essentially  of  a  spectrophotometer 
with  an  additional  arm  to  permit  the  admixture  of  a  known 
amount  of  white  light.  Briefly  stated,  the  hue  of  the  sub- 
ject is  matched  by  varying  the  angular  position  of  one  arm, 
the  purity  is  matched  by  varying  the  amount  of  white  light 
added,  on  the  principle  that  any  hue  can  be  matched  by 
mixing  white  light  in  suitable  proportion  with  the  corre- 
sponding spectral  hue,  and  the  brightness  is  measured  by 
the  photometer  attachment. 

By  means  of  these  two  instruments  it  is  possible  com- 
pletely to  analyze  a  color,  and  to  state  the  color  in  terms  of 
figures  for  the  constants,  hue,  purity,  and  brightness.  Need- 
less to  say,  the  use  of  figures  as  a  measure  of  color  in  the  arts 
should  be  accompanied  by  the  use  of  plus  and  minus  limits, 
as  in  dimensional  work.  Quality  varies  in  the  case  of  color 
just  as  it  does  in  dimensional  work,  and  the  same  phenomena 
must  be  met  by  practices  alike  in  principle.  The  precision 
used  will  vary  with  the  character  of  the  commercial  require- 
ments for  the  given  case  and  with  the  economic  and  techni- 
cal possibilities  of  the  processes. 

The  spectroscopic  type  of  instrument  is  available  for 
control  laboratory  purposes.  This  apparatus  may  be  used 
as  a  guide  in  the  control  of  quality  of  basic  materials,  such  as 
dyestuffs  and  pigments,  and  for  the  completed  product, 
with  this  qualification  that  many  of  the  colors  used  in  the 
arts  are  what  are  known  as  "mode"  or  "fashion"  colors, 
most  of  which  are  quite  dark.  A  great  many  textiles,  for 
example,  reflect  less  than  5  per  cent  of  the  incident  light  and 
it  is  difficult  to  get  precise  measurements  with  instruments 
which  themselves  absorb  a  quantity  of  light  in  the  optical 
parts.  A  sufficiently  intense  demand  from  the  arts  will 
doubtless  bring  about  the  development  of  instruments  of 


THE  CONTROL  OF  COLOR  365 

this  sort  more  suitable  for  general  application  and  in  which 
the  light  from  a  larger  area  is  concentrated  in  order  to 
provide  sufficient  light  to  analyze  and  measure  with  ease  and 
precision.  There  is  need  also  for  an  instrument  which  will 
more  readily  permit  of  analyzing  color  in  terms  of  the  re- 
agents used  to  create  that  color.  Such  an  instrument  also 
will  be  merely  an  improved  adaptation  of  existing  instru- 
ments and  will  be  used  in  conjunction  with  a  technique  for 
working  out  quantitatively  the  combinations  of  pigments, 
dyes,  or  stains  required  to  produce  a  given  color  effect. 

Auxiliary  Instruments 

A  number  of  devices  are  available  in  which  the  method 
of  analysis  consists  in  filtering  through  monochromatic 
filters.  It  should  be  observed,  however,  that  such  instru- 
ments do  not  analyze  color  in  terms  of  hue,  purity,  and 
brightness  as  the  eye  sees  color.  They  are,  nevertheless, 
suited  to  certain  applications  in  the  arts,  although  they  do 
not  give  the  same  complete  range  of  measurement  obtain- 
able by  the  use  of  the  spectrophotometer. 

A  useful  instrument  for  many  sorts  of  industrial  purposes 
is  known  as  the  Hess-Ives  Tint-Photometer.  With  this 
instrument  it  is  possible  to  take  readings  of  a  subject  as  a 
percentage  of  the  light  reflected  from  a  block  of  magnesia, 
and  to  compute  the  brightness  therefrom.  For  bright  flat 
colors,  such  an  instrument  yields  a  measurement  of  the 
color  in  terms  of  the  primaries,  red,  green,  and  blue-violet, 
expressed  as  percentages  of  light  taken  through  the  same 
filters  from  the  100  per  cent  magnesia  standard. 

Other  filters  are  provided  for  special  industrial  uses. 
For  the  darker  shades  or  mode  colors  the  measurements 
would  be  less  than  5  per  cent  and  hence  would  be  useless 
for  practical  purposes.  For  work  of  this  sort,  a  neutral 
gray  standard  may  be  constructed  for  use  instead  of  the 


366  THE  CONTROL  OF  QUALITY 

magnesia  block,  care  being  taken  to  see  that  the  new  stand- 
ard is  a  true  gray.  It  may  be  made  by  mixing  lamp  black 
with  magnesia  (carbonate  or  oxide).  The  use  of  a  gray 
standard  will  throw  the  measurement  well  up  into  the  scale. 
The  author  had  used  such  standards  which  reflected  less 
than  10  per  cent  of  the  magnesia  standard  and  consequently 
multiplied  the  scale  readings  by  10  or  more.  The  instru- 
ment may  be  used  also  for  direct  comparisons  between  a 
standard  sample  and  the  unknown  subject. 

Reduction  of  Errors  in  Color  Work 

Those  who  are  interested  in  color  work  in  industry  would 
do  well  to  make  a  close  study  of  the  phenomena  involved 
from  the  physical  standpoint,  i.e.,  the  study  of  color  from  the 
standpoint  of  light.  Such  a  study  should  reveal  the  need 
of  a  more  definite  and  precise  terminology,  the  desirability 
of  measurement  in  all  its  applications,  and  for  the  evolution 
of  simple  measuring  apparatus,  as  well  as  of  evolving  appa- 
ratus more  nearly  suited  to  the  needs  of  applied  science. 

When  instrumental  means  are  not  used,  inspectors  in 
color-matching  should  be  checked  by  actual  test,  even  if 
more  exact  methods  are  not  available.  In  this  manner,  the 
dangers  of  large  personal  errors  due  to  idiosyncrasies  of 
color  vision  may  be  minimized.  Everyone  working  with 
color  should  be  warned  against  the  errors  due  to  contrast, 
and  instructed  in  the  relief  of  eye  fatigue,  caused  by  looking 
at  brilliant  red,  for  example,  by  such  a  simple  expedient  as 
an  occasional  glance  at  an  equally  brilliant  green.  The 
value  of  standardized  matching  lights  would  hardly  seem 
to  need  mentioning. 

Such  a  study  as  that  recommended  will  reveal  industry's 
great  need  for  the  measurement  of  color  in  terms  of  figures. 
The  possibilities  for  resulting  economy  in  the  arts  are  aston- 
ishing. 


THE  CONTROL  OF  COLOR  367 

Standards  of  Appearance 

Needless  to  say  the  extension  of  the  same  precise  con- 
trol scheme  to  other  industrial  problems  besides  color  holds 
forth  interesting  opportunities  for  reducing  errors  and 
minimizing  losses.  It  is  not  at  all  unlikely  that  a  similar 
application  of  optical  methods  may  be  profitably  developed 
to  reduce  various  sorts  of  finishes,  such  as  polished  metal 
surfaces,  to  a  basis  of  definite  standardization.  Optical 
instruments  of  other  sorts  have  already  been  used  exten- 
sively in  a  variety  of  industrial  applications  (e.g.,  the  sugar 
and  oil  industries)  and  it  is  only  reasonable  to  expect  the 
adoption  of  such  methods  in  other  fields. 

Appearance,  as  previously  indicated,  is  in  reality  nothing 
but  light,  but  the  qualities  of  this  light  which  characterize 
a  given  appearance  may  be  caused  by  a  variety  of  things, 
such  as  the  finish  and  texture  of  the  surface,  for  example. 
That  is  to  say,  color  is  but  one  of  the  qualities  which  go  to 
make  up  appearance;  nevertheless,  all  of  these  qualities 
are  subject  to  the  same  general  treatment  of  analysis  (both 
qualitative  and  quantitative),  followed  by  the  ascertain- 
ment of  the  relations  between  the  final  results  and  the 
causes  thereof — in  short,  by  the  usual  methods  of  science. 


CHAPTER  XXII 

THE  SCIENTIFIC  ATTITUDE  OF  MIND 
AND  ITS  METHODS 

Science  and  the  Arts 

It  is  usual  for  the  people  of  the  present  day  to  observe 
with  pride  the  progress  made  in  the  arts  and  sciences  during 
the  last  century — a  story  of  advances  greater  probably  than 
in  all  previous  time,  and  made  at  a  rate  that  is  still  accelerat- 
ing. There  are  one  or  two  aspects  of  this  situation  which 
are  not  so  much  of  historical  interest  as  they  are  of  value  in 
pointing  the  surest  way  to  further  and  more  rapid  progress, 
especially  in  the  manufacturing  arts. 

The  first  of  these  thoughts  is  that  the  recent  rapid  im- 
provements in  industry  are  dependent  upon  and  followed 
after  a  great  advance  in  the  sciences.  As  Jevons  says : 

A  science  teaches  us  to  know,  and  an  art  to  do,  and  all  the  more 
perfect  sciences  lead  to  the  creation  of  corresponding  useful  arts. 
Astronomy  is  the  foundation  of  the  art  of  navigation.  .  .  . 

The  industrial  arts  have  existed  on  a  broad  scale  for 
ages,  but  in  former  times  science  shows  only  as  a  dim  light, 
from  time  to  time  and  in  scattered  places.  Modern  manu- 
facturing followed  the  wonderful  scientific  movement  which 
began  in  force  but  a  few  generations  ago ;  it  has  progressed 
only  so  far  as  it  has  applied  these  scientific  discoveries. 

The  second  and  somewhat  startling  thought  is  that  the 
arts,  in  large  part  at  least,  have  whole-heartedly  and  strenu- 
ously resisted  every  attempt  to  introduce  and  apply  the 
discoveries  of  science.  Everyone  is  quite  inured  to  the 
attitude  of  labor  leaders  in  opposing  the  adoption  of  labor- 
saving  devices,  in  spite  of  the  fact  that  the  greatest  hope 

368 


THE  SCIENTIFIC  ATTITUDE  OF  MIND  369 

of  the  rank  and  file  for  a  greater  share  of  the  good  things  of 
this  world,  lies  in  the  production  of  more  goods  and  better 
goods,  with  less  effort.  And  the  extra  effort  thus  released 
is  available  to  produce  still  other  things  which  never  ex- 
isted before.  This  attitude  is  an  old  story  and  a  stupid 
one,  but  it  is  not  entirely  what  is  referred  to  here.  For  the 
source  of  much  opposition  to  the  adoption  of  improve- 
ments, or  in  fact  of  any  conscious  preplanned  program  for 
advancing  industry,  is  to  be  found  in  the  attitude  of  indus- 
trial executives,  from  foreman  to  manager  to  owner — es- 
pecially the  latter,  or  scientific  workers  would  be  better  paid. 

Science  and  the  Practical  Man 

In  short,  there  exists  the  contradiction  that  industry 
owes  its  present  high  position  to  science,  but  industry 
habitually  opposes  further  improvement.  Industry,  how- 
ever, will  agree  with  one  of  science's  principles,  namely, 
that  there  must  be  a  cause  for  every  effect.  That  being  so, 
there  must  be  a  cause  for  such  a  situation ;  which  leads  quite 
naturally  to  the  conclusion  that  it  ought  to  be  worth  the 
time  and  trouble  to  consider  this  matter  rather  carefully. 
Perhaps  the  inquiry  may  result  in  working  out  a  compro- 
mise attitude  of  service  to  both  parties. 

It  must  be  admitted  at  once  that  conservatism  is  a  useful 
thing,  provided  it  is  not  reactionary.  Sane  opposition  to 
change  is  doubly  valuable.  If  men  rushed  to  adopt  every 
new  device  without  careful  consideration  and  practical 
test,  we  should  all  be  living  in  the  chaos  of  Sovietism,  if  we 
succeeded  in  holding  ourselves  even  at  that  level.  Further- 
more, opposition  to  change  is  necessary  to  secure  the  ad- 
vantage of  the  change.  Newton  said  this  in  his  third  law 
of  motion — " Action  and  reaction  are  equal  and  opposite." 
A  force  requires  something  to  push  against  in  order  to 
build  up  its  potential;  and  the  opposition  which  must  be 

24 


370  THE  CONTROL  OF  QUALITY 

overcome  is  the  thing  which  develops  real  strength  in  any 
movement.  Thus  the  measure  of  your  belief  in  a  principle 
depends  upon  and  varies  with  your  willingness  to  fight  for 
it.  With  this  realization,  you  will  prepare  yourself  better 
to  convince  people  that  your  plans  are  correct  and  to  per- 
suade them  that  your  ideas  should  be  adopted.  To  do  so, 
you  must  be  thorough  in  your  own  preparation,  which  will 
result  in  having  something  better  to  sell  than  you  had  at 
first.  In  fact,  a  reasonable  disagreement  is  encouraging 
because  if  everyone  accepted  what  you  said  at  once  and 
without  discussion,  you  would  have  nothing  new  or  worth 
while  after  all. 

In  the  factory,  however,  one  often  encounters — perhaps 
I  should  say,  one  usually  and  very  certainly  encounters- 
something  that  is  more  than  just  conservatism.  This  at- 
titude is  the  particular  hobby  of  the  "practical"  man,  who 
takes  genuine  pride  in  being  out  of  patience  with  all  "the- 
ory." In  the  extreme  form  this  type  of  factory  executive 
recalls  Lord  Beaconsfield's  definition  of  a  practical  man  as 
one  who  practices  the  errors  of  his  forefathers.1  This  at- 
titude of  mind  can  be  spotted  at  once,  by  recommending 
some  slight  improvement  or  change  in  method  of  carrying 
out  a  process.  The  "practical"  man  will  assert  that  he  has 
been  doing  it  successfully  as  it  is  for  the  last  twenty  years 
(thirty-five  is  a  favorite  figure  also) ;  and  will  then  talk 
about  his  experience.  The  best  way  to  meet  this  attitude 
is  by  education — proving  the  point  by  teaching,  step  by 
step.  It  sometimes  requires  almost  infinite  patience  to 
save  such  a  man  from  himself. 

Theory  or  Theorists 

In  all  fairness,  it  must  be  said  that  there  is  a  good  deal  of 
justification  for  the  practical  man's  rejection  of  theory,  and 

1  "An  Introduction  to  Mathematics,"  by  A.  N.  Whitehead  (p.  40). 


THE  SCIENTIFIC  ATTITUDE  OF  MIND  371 

especially  of  theorists.  The  man  who  has  the  job  of  mak- 
ing things  has  to  confine  his  interest  to  proved  methods; 
his  business  does  not  provide  time  for  speculation  or  ex- 
perimentation in  working  hours.  When  goods  produced 
is  the  measure  of  achievement,  as  it  must  and  should  be  in 
the  shop,  there  is  bound  to  be  objection  to  even  taking  a 
chance  of  failure.  Such  losses  should  be  confined  to  the 
laboratory,  which  should  be  kept  separate  from  the  shop  for 
that  reason. 

Too  often  also,  the  charge  is  true  that  the  scientific 
worker  is  wholly  out  of  touch  with  the  practical  details  of 
the  arts  which  should  depend  upon  his  work  for  their  future 
progress.  The  scientist  finds  some  measure  of  explanation, 
when  this  situation  exists,  both  because  his  work  is  apathet- 
ically received  by  the  practical  man,  as  well  as  because  he 
is  professedly  in  search  of  knowledge  for  its  own  sake  rather 
than  for  its  immediate  money  value.  ' '  There  is  a  necessary 
unworldliness  about  a  sincere  scientific  man;  he  is  too  pre- 
occupied with  his  research  to  plan  and  scheme  how  to 
make  money  out  of  it."2  His  greatest  compensation  lies 
in  the  realization,  as  Dr.  George  Sarton  has  so  ably  said,3 
that  man's  intellectual  advancement  is  the  only  real  meas- 
ure of  progress.  Anything  which  helps  to  solve  the  ever- 
present  problems  which  the  world  offers,  means  progress 
to  the  true  man  of  science.  If  the  solution  is  not  useful 
now,  it  will  be  later  on;  and,  if  in  the  meantime  he  can  carry 
on  in  his  chosen  field  only  at  great  personal  sacrifice,  then 
all  the  more  reason  to  speak  the  truth  at  any  personal  cost 
and  to  worry  little  about  the  criticism  or  opposition  of  the 
moment. 

There  is  evidence  on  all  sides  of  a  lack  of  correlation  of  the 
sciences  and  the  arts  which  doubtless  is  due  to  the  difficulty  an 


'•  "The  Outline  of  History,"  by  H.  G.  Wells. 

3  See  his  essays  in  Scribner's  on  "  The  Message  of  Leonardo  "  and  "  Hidden  History." 


372  THE  CONTROL  OF  QUALITY 

individual  encounters  in  adapting  himself  to  these  two  viewpoints. 
For  the  benefit  of  his  art,  the  artist  should  acquaint  himself  with  the 
general  sciences  upon  which  his  art  is  founded ;  and  for  the  benefit  of 
progress  the  scientist  should  bear  in  mind  the  viewpoint  of  the  artist. 
There  should  be  no  misapprehension  regarding  the  relation  of  science 
and  art,  because  the  former  supplies  the  enduring  foundation  of  the 
latter.  For  this  reason  it  appears  that  those  who  primarily  possess 
a  scientific  viewpoint  should  attempt  to  bridge  the  gap  by  laying  their 
course  upon  facts.4 

The  Engineer  as  Co-ordinator 

Granting  that  nothing  but  good  can  come  from  bridging 
the  gap  between  science  and  industry,  the  only  question  to 
be  answered  is —  "Who  is  the  man  to  do  it?"  The  engineer, 
either  as  executive  or  consultant,  logically  seems  the  man 
for  the  job.  He  either  is  or  should  be  pretty  close  to  both 
sides.  If  he  is  a  real  engineer  he  must  be  a  fairly  good 
scientist.  If  he  is  of  any  use  in  the  manufacturing  plant  he 
must  be  practical  in  his  viewpoint.  As  the  friend  of  pro- 
duction, he  will  analyze  its  needs  for  science's  help,  and  in 
the  light  of  a  sympathetic  understanding  bred  of  contact 
with  the  work.  His  observation,  moreover,  will  be  guided 
by  a  knowledge  and  appreciation  of  the  methods  of  science, 
and  his  acquaintance  with  science  will  tell  him  where  to 
look  for  further  guidance.  Once  he  knows  the  answer,  his 
real  task  is  to  put  it  into  form  for  practical  use,  and  to  make 
clear  and  convincing  explanation  of  its  fine  points  and  ad- 
vantages to  the  man  who  must  do  the  actual  work. 

The  engineer's  purpose  in  industry  should  be  to  save 
effort  by  making  it  possible  to  do  the  job  in  hand  more 
easily,  and  with  a  better  product  for  a  given  effort.  There 
are  so  many  things  to  be  done  which  have  not  even  been 
started  yet,  that  it  is  greatly  to  everyone's  interest  to  free 
ourselves  from  just  as  much  effort  in  doing  our  present  work 

4  From  the  introduction  to  "The  Language  of  Color,"  by  M.  Luckiesh,  Director  of  Ap- 
plied Science,  Nela  Research  Laboratories,  National  Lamp  Works  of  the  General  Electric  Co., 
Cleveland. 


THE  SCIENTIFIC  ATTITUDE  OF  MIND  373 

as  we  possibly  can.  To  carry  out  this  project  in  syste- 
matic form  requires  recognition  of  the  fact  that  material 
progress  rests  upon  an  intellectual  foundation;  and,  as  we 
have  seen,  this  in  turn  receives  its  greatest  impetus  from  a 
peculiar  mental  attitude  or  method  of  thinking  which  is 
known  as  "scientific."  Let  us  consider  some  of  the  special 
characteristics  of  this  attitude. 

The  Scientific  Attitude 

Every  small  boy,  unless  he  is  most  unlucky,  passes 
through  the  stage  of  learning,  rather  early  in  his  career, 
that  he  gains  nothing  by  lying,  crookedness,  or  not  playing 
fair.  Seemingly  men  have  had  to  go  through  with  much 
the  same  process  in  their  constant  fight  with  nature.  The 
world  is  a  pretty  decent  place  if  we  are  careful  to  conform  to 
nature's  laws,  but  we  are  sure  of  defeat  when  we  do  not. 
The  bridge  that  is  designed  to  suit  a  present  fancy,  instead 
of  being  in  strict  conformity  with  the  established  laws  of 
statics  and  the  proved  strength  of  its  materials,  is  certain 
to  fail.  All  engineering  practice  owes  its  rapid  progress  to 
the  truthful  observance  of  and  strict  adherence  to  known 
principles  and  proved  facts. 

There  are  several  ways  in  which  such  a  body  of  knowl- 
edge can  be  secured,  and  when  systematized  into  form  for  use 
it  may  be  called  ' 'science."  If  this  knowledge  is  obtained 
by  the  slow  and  expensive  process  of  trial  and  error  in 
actual  practice,  each  success  provides  an  indication  of  one 
limiting  condition  and  each  failure  shows  another  limit; 
but  the  method  can  hardly  be  called  scientific.  That  is  the 
old  method  by  which  the  arts  used  to  advance.  What 
special  features  distinguish  the  newer  method  ? 

One  of  the  most  obvious  distinctions  is  that  science  is 
not  satisfied  merely  to  know  that  such  and  such  a  thing  is 
true — it  must  know  why.  That  the  ultimate  why  is  un- 


374  THE  CONTROL  OF  QUALITY 

knowable  merely  adds  zest  to  the  game — it  extends  our 
horizon  to  the  limits.  Having  discovered  why,  we  are  in 
a  position  to  extend  the  application  of  the  principle  in- 
volved. Without  knowing  why,  we  could  only  repeat  what 
had  been  done  before.  Thus  the  search  for  knowledge  in 
the  form  of  principles  of  general  application  is  one  of  the 
chief  characteristics  of  the  scientific  method.  Its  most 
obvious  application  in  manufacturing  is  to  know,  in  detail, 
the  principles  involved  in  the  processes  in  use  in  the  factory. 
Upon  what  elementary  laws  of  nature  do  they  depend,  and 
what  special  adaptations  of  such  laws  are  involved  ?  Look 
around  you  and  see  how  many  processes  there  are  not,  whose 
true  inwardness  is  known.  Many  of  the  oldest  will  be 
found  in  this  class.  The  latest,  such  as  those  peculiar  to 
electrical  work,  have  been  able  to  profit  by  the  discoveries 
of  the  science  which  made  them  possible.  Even  the  proc- 
esses we  think  we  know  something  about,  still  provide 
room  for  intensive  study;  which  brings  us  to  another  char- 
acteristic of  this  special  sort  of  mental  attitude. 

The  scientist  approaches  his  problem  with  humility. 
Constant  pondering  over  natural  phenomena  can  have  no 
other  effect  than  to  make  clear  the  huge  number  and  vast 
range  of  the  knowable  things  which  we  still  have  to  find 
out  about.  Against  such  a  background,  what  we  today 
call  knowledge  seems  puny  indeed.  In  this  realization 
lies  one  of  the  scientist's  greatest  sources  of  power.  Know- 
ing how  little  he  knows,  he  makes  very  sure  to  see  that  his 
work  is  done  with  such  precision  that  error  is  reduced  to  a 
minimum.  He  pays  great  attention  to  minute  details,  so 
that  nothing  shall  be  left  out,  because  the  answer  may  lie 
in  some  insignificant  fact  which  is  obscured  by  its  very 
obviousness.  Nothing  is  taken  for  granted,  and  although 
influenced  by  practical  experience,  he  is  careful  to  avoid  its 
dangers  by  freeing  his  mind  of  traditional  untruths. 


THE  SCIENTIFIC  ATTITUDE  OF  MIND  375 

The  Scientific  Method 

However  humble  the  scientific  man's  attitude  in  pre- 
paring his  mind  to  attack  his  problems,  he  nevertheless 
goes  into  action  with  confidence  of  success,  because  he  has 
a  method  which  works.  Applied  with  determination  and 
guided  by  good  judgment,  the  scientific  method  is  the  one 
method  that  is  certain  to  produce  results  sooner  or  later. 
For  its  guiding  principle  is  fidelity  to  truth,  and  in  this  sense 
the  achievements  of  scientific  research  are  the  greatest  pos- 
sible vindication,  in  practical  form,  of  the  great  moral  law 
of  honesty,  in  its  broadest  application.  This  is  the  first 
thought  which  should  be  driven  home  to  every  student  of 
the  engineering  sciences.  There  is  but  one  safe  way  to  deal 
with  natural  phenomena,  namely,  to  make  sure,  with  pain- 
ful accuracy,  that  your  facts  are  correct  and  complete,  also 
that  the  conclusions  drawn  from  these  facts  are  sound  in 
every  particular.  Then,  if  the  principles  and  practices 
thus  developed  are  translated  into  action  with  the  same 
fidelity  to  truth,  really  useful  results  are  sure  to  follow. 
The  success  of  any  other  method  is  a  matter  of  chance. 

In  the  effort  to  present  in  convincing  form  conclusions 
reached  by  the  scientific  method,  the  engineer  would  do  well 
to  take  a  leaf  from  the  book  of  the  lawyer,  who  must  neces- 
sarily make  very  sure  of  the  truth  and  completeness  of  his 
facts,  and  be  certain  that  his  deductions  are  both  logical 
and  precise.  The  literature  on  argumentation  and  the  very 
practical  methods  for  testing  evidence  and  building  briefs 
contain  many  useful  hints  which  the  engineer  may  adapt  to 
his  situation  with  profit.  Not  the  least  of  these  is  the  way 
in  which  the  lawyer  deals  with  the  technical  and  scientific 
matters  which  arise  within  his  purview.  Realizing  his  own 
ignorance,  he  first  makes  sure  to  learn  the  story  himself. 
Then  he  assumes  an  equal  ignorance  on  the  part  of  his 
readers  and  writes  a  clearer  exposition  and  more  convincing 


376  THE  CONTROL  OF  QUALITY 

presentation  of  the  technical  matters  involved  than  does 
the  discoverer  of  these  very  phenomena. 

Then  again,  scientific  work  yields  high  returns  for  con- 
structive imagination.  The  latter  is  one  of  the  rarest  and 
least  used  of  the  mental  processes,  yet  because  of  its  for- 
ward-looking attitude  it  should  be  strongly  developed.  The 
mere  statement  that  something  is  good  enough  as  it  is,  or 
that  further  improvement  is  impossible,  should  be  a  sure 
sign  to  the  engineer  that  right  there  is  an  opportunity. 
The  situation  may  call  for  all  his  ingenuity,  and  surely  for 
plenty  of  hard  thinking.  All  the  anticipatory  and  con- 
structive imagination  he  possesses  may  well  be  focused  on 
the  problem;  but  if  this  follows  a  thorough  and  truthful 
analysis  of  the  problem  in  the  first  place,  his  hard  work  and 
late  hours  will  be  amply  rewarded  by  results  of  practical 
value. 

The  Place  of  the  Engineer 

The  reason  for  inviting  attention  to  the  preceding  dis- 
cussion of  the  scientific  attitude  of  mind  and  its  methods, 
is  to  indicate  the  way  in  which  we  should  go  about  the  ad- 
vancement of  the  arts  of  manufacturing.  The  most  suc- 
cessful method  is  obvious.  It  remains  only  to  select  the 
man  to  direct  the  job,  because  without  a  definite  assign- 
ment and  a  systematic  program  we  shall  get  nowhere. 
"  Everybody's  business  is  nobody's  business." 

As  already  stated,  the  technically  trained  engineer  is 
the  logical  co-ordinator  of  science  and  industry.  Atten- 
tion is  directed  to  the  phrase  "technically  trained,"  because 
some  men  go  through  college  without  achieving  that  result, 
and  others  acquire  education  without  going  to  college  at  all. 
But  the  man  must  be  an  engineer  in  the  truest  sense,  regard- 
less of  the  route  by  which  he  has  arrived  at  that  specialized 
intellectual  condition. 


CHAPTER  XXIII 

THE      METHOD      OF     ATTACK     TO      CONTROL 

QUALITY 

The  Approach  to  the  Problem 

There  is  a  lesson  for  everyone  contained  in  the  Chinese 
philosophy  which  says  that  no  theory  has  any  value  except 
in  so  far  as  it  is  translated  into  action  or,  at  least,  is  trans- 
latable into  action.  Therefore  if  there  is  any  merit  in  this 
theory  of  controlling  quality,  completeness  requires  that 
some  plan  be  advanced  for  approaching  the  task  of  bringing 
quality  under  control. 

Since  quality  of  output  is  the  ultimate  result  of  tech- 
nical processes  in  one  form  or  another,  it  follows  that  the 
best  way  of  solving  problems  in  the  control  of  quality  is  to 
use  the  scientific  method.  It  is  the  best  method  for  ob- 
taining rapid  and  certain  returns.  But  it  must  be  applied 
in  a  strictly  practical  engineering  way  because  this  is  a  com- 
mercial application  of  the  method  rather  than  a  purely 
scientific  search  after  knowledge  for  its  own  sake.  The 
sort  of  knowledge  wanted  in  this  instance  must  be  of  im- 
mediate and  economic  use. 

Uniformity  within  Limits 

In  crystallized  form,  the  underlying  object  of  any 
manufacturing  enterprise  is  to  make  more  and  better  goods 
for  less  money — to  obtain  a  greater  output  of  standard 
quality  for  less  effort.  In  planning  to  bring  quality  under 
control,  therefore,  every  step  is  made  with  a  view  to  re- 
moving obstacles  to  greater  and  better  output  by  regulating 
the  deviations  from  standard.  In  every  instance  these 

377 


378  THE  CONTROL  OF  QUALITY 

deviations  or  errors  represent  losses  in  the  use  of  material, 
labor,  and  manufacturing  plant.  Perfect  quality  implies 
freedom  from  errors.  But  there  is  a  limit  to  which  quali- 
tative refinement  can  be  carried  with  economy.  Conse- 
quently, while  it  is  true  that  we  seek  uniformity,  it  is  a 
modified  and  reasonable  degree  of  uniformity — that  is, 
uniformity  within  commercial  limits.  The  economy  of 
manufacture  requires  that  the  limits  be  suitable  for  the 
case  in  hand  at  the  moment — they  must  not  be  too  large  or 
too  small. 

The  scientific  method  is  to  be  applied,  then,  to  manu- 
facturing problems  with  quality  as  the  criterion,  but  every 
solution  worked  out  in  this  way  must  be  mentally  projected 
against  a  background  of  dollars  and  cents,  and  our  conclu- 
sions modified  accordingly  to  suit  the  present  commercial 
situation. 

Getting  the  Facts 

In  applying  any  such  method  to  a  given  industrial  situ- 
ation the  first  desideratum  would  appear  to  be  an  unbiased 
scrutiny  of  the  business  as  it  is.  The  art  of  seeing  things  as 
they  really  are  is  often  a  gift,  but  it  can  be  cultivated  also. 
The  industrial  executive  is  so  close  to  the  details  of  the 
business  that  the  most  obvious  things  escape  him.  Unless 
he  recognizes  this  failing  and  stops  to  take  stock  of  the 
situation  he  is  very  apt  to  get  into  a  fix  where  "he  can't  see 
the  woods  for  the  trees."  Yet  an  accurate  viewing  of  the 
problem  is  prerequisite  to  any  measure  of  success  in  laying 
out  a  program  for  constructive  work. 

A  prominent  manufacturer  who  has  a  faculty  for  con- 
cise expression  says  that  industry  should  heed  the  warning 
of  his  boyhood  riding-master.  The  latter  was  in  the  habit 
of  concluding  his  advice  about  sitting  up  straight  and  so  on, 
by  barking  out — "Get  off  your  horse  and  look  at  yourself 


THE  METHOD  OF  ATTACK  379 

riding."  Many  a  factory  would  be  the  better  if  its  con- 
trolling executives  would  get  off  their  horses  and  watch 
themselves  riding — they  wouldn't  look  so  humped  up  to  the 
disinterested  outside  observer. 

But  after  all,  isn't  this  just  another  way  of  starting  in  to 
practice  the  things  we  have  been  considering  in  the  last 
chapter?  As  we  have  just  observed,  one  of  the  outstanding 
features  of  the  scientific  method  is  the  collection  of  basic 
data,  and  the  testing  of  such  data  to  make  sure  that  it  is 
correct;  so  that  the  first  step  is  to  get  the  facts  in  the  case — 
starting  with  the  general  business  situation  and  its  trends  as 
affecting  quality,  and  then  in  all  the  detailed  ramifications 
of  the  business  itself.  The  first  or  general  viewing  has  to 
do  with  external  or  commercial  relationships,  while  the  de- 
tailed study  is  for  the  most  part  a  matter  of  regulating 
conditions  within  the  factory. 

Analysis 

In  securing  the  facts  in  detail  it  soon  becomes  evident 
that  resort  must  be  had  to  analysis.  Manufacturing  prob- 
lems are  too  large  to  be  solved  as  a  whole  and  must  be 
broken  up  into  parts  which  are  small  enough  to  suit  the 
limitations  of  our  intellectual  equipment.  Getting  the 
facts  is  often  the  hardest  part  of  the  entire  process,  and  the 
way  in  which  the  preliminary  analysis  is  made  becomes  of 
great  importance. 

Of  course  there  is  no  exact  and  arbitrary  scheme  of 
analysis  which  can  be  rigorously  applied  to  every  case,  but 
certain  general  guides  should  be  followed,  just  as  in  the 
case  of  collecting  and  testing  legal  evidence.  The  first  step 
is  to  make  sure  that  we  have  all  the  facts  and  that  they  are 
facts — to  test  their  truth.  The  next  step  is  to  exclude  those 
which  are  clearly  not  pertinent  to  the  problem  in  hand,  as 
well  as  those  which  obviously  are  of  such  little  influence  as 


380  THE  CONTROL  OF  QUALITY 

to  be  unworthy  of  consideration.  Finally,  the  remaining 
data  should  be  measured  to  determine  the  influence  (and 
the  relative  influence)  of  each  fact  upon  the  problem  as  a 
whole.  Thus  measurement  takes  its  place  as  a  part  of 
analysis,  or  more  accurately,  as  a  necessary  accompani- 
ment to  analysis. 

Tripartition  or  Tripartite  Analysis 

Since  there  appears  to  be  no  generally  accepted  scheme 
for  making  sure  that  an  analysis  is  complete  and  that  all 
pertinent  facts  have  been  collected,  I  am  venturing  to  sug- 
gest the  use  of  a  general  guide  or  working  rule  which  has 
proved  of  value  in  personal  work.  This  working  rule  is  that 
any  complete  analysis  should  be  made  from  three  principal 
viewpoints  (or  from  at  least  three  different  angles).  Its 
practical  application  works  in  this  fashion — if  you  have 
examined  a  question  from  only  one  or  two  points  of  view, 
there  probably  is  something  missing;  hence  at  least  one 
more  division  of  the  subject  should  be  made.  On  the  other 
hand,  in  ordinary  practice  three  main  divisions  of  the  sub- 
ject are  enough. 

For  example,  it  has  been  fashionable  for  labor  and  capi- 
tal to  consider  themselves  as  solely  interested  in  so-called 
labor  problems,  whereas  both  sides  to  the  controversy 
would  have  done  well  to  consider  the  interests  of  the  great 
third  party — the  public — which  in  this  case  holds  the  decid- 
ing vote.  Another  example  more  closely  related  to  the 
work  in  hand  is  to  be  found  in  the  common  error  of  assum- 
ing that  any  cause  has  but  one  effect.  The  truth  is  that 
every  cause  has  several  effects.  As  a  simple  instance  of 
this,  suppose  that  a  greater  output  is  sought  by  the  means 
of  providing  a  high  incentive  in  the  form  of  a  greatly  in- 
creased piece  rate.  The  cause  (one  element)  is  the  higher 
incentive;  the  direct  effect  (the  second  element)  is  greater 


THE  METHOD  OF  ATTACK  381 

output,  but  unless  the  accompanying  additional  effects 
(the  third  element)  are  considered  and  arranged  for,  the 
quality  of  the  output  will  drop.  Consequently,  a  complete 
analysis  would  provide  at  the  start,  with  tripartition  as  a 
guide,  for  an  adequate  stiffening  of  the  provisions  for  in- 
spection as  a  means  of  controlling  quality  to  the  desired 
standards. 

It  may  be  mentioned  incidentally  and  as  a  matter  of 
interest  that  I  adopted  this  tripartite  guide  in  analytical 
work  after  observing  the  frequency  with  which  careful 
thinkers  divide  their  subjects  into  three  main  sections.  A 
little  consideration  will  show,  however,  that  there  is  a  basis 
for  the  method  in  the  physical  world  all  about  us.  Thus 
the  three  physical  constants  generally  used  as  a  foundation 
for  measurement  are  mass,  time,  and  space,  each  one  of 
which  (and  many  other  physical  things)  again  divides  into 
three  elements. 

The  use  of  the  three  divisions  of  time  (i.e.,  past,  present, 
and  future)  will  be  found  very  useful  in  the  analysis  and 
subsequent  solution  of  many  factory  problems.  This 
time  relationship  as  affecting  the  planning,  production,  and 
inspection  groups  in  organization  has  been  traced  in  Chapter 
V.  It  may  often  be  utilized  in  the  study  of  an  individual 
process.  For  example,  deviations  from  standard  may  be 
caused  in  the  process  itself;  or  they  may  be  carried  over 
from,  or  result  from  some  cause  in  a  previous  process;  or 
they  may  even  be  due  to  the  influence  of  a  subsequent 
process.  All  three  possibilities  should  be  considered. 
Thus,  if  the  later  processes  are  in  need  of  work,  the  workers 
whose  operation  is  in  trouble  may  be  unduly  hurried;  or 
they  may  be  assuming  that  any  errors  they  make  will  be 
corrected  by  subsequent  and  more  precise  operations. 
This  third  element  (the  possible  influence  of  later  opera- 
tions) is  too  frequently  overlooked. 


382  THE  CONTROL  OF  QUALITY 

The  subject  of  color  quality  has  been  treated  in  Chap- 
ter XXI  in  accordance  with  the  tripartite  guide. 

Quality  Records 

The  basic  data  for  analysis  will  be  obtained  from  various 
sources.  Such  production  and  cost  records  as  are  at  hand 
should  be  used  as  a  starting  point,  but  it  generally  will  be 
found  that  the  facts  presented  by  such  records  are  not 
sufficient  nor  are  they  arranged  in  the  most  useful  form  for 
the  study  of  quality  problems.  As  noted  in  Chapter  VI, 
a  well-organized  inspection  service  is  a  very  useful  instru- 
mentality for  the  collection  of  facts  relating  to  quality. 
But  a  preliminary  analysis  should  be  made  and  used  as  a 
basis  for  the  quality  records. 

Since  quality  involves  uniformity  within  limits,  the 
control  of  quality  requires  that  quality  records  deal  with 
variations  from  the  working  standards.  They  must  show 
where  and  when  these  variations,  or  manufacturing  errors, 
occur.  This  involves  an  analytical  list  of  all  the  kinds  of 
errors  which  do  occur.  They  must  show  for  each  kind  of 
error  the  relative  frequency  of  its  occurrence,  and,  in  a 
general  way  at  least,  the  size  of  the  individual  errors — all  of 
which  involves  some  form  of  measurement. 

Quality  records,  then,  should  present  a  list  of  character- 
istic qualities,  a  list  of  the  kinds  of  error  for  each  quality,  a 
statement  of  the  number  and  sizes  of  each  kind  of  error, 
and  a  notation  of  when  and  where  the  error  occurs.  The 
cause  of  the  error  should  be  added  if  known,  but,  strictly 
speaking,  the  determination  of  causes  is  a  matter  for  sub- 
sequent treatment.  And  all  of  the  data  is  a  subject  for 
treatment  by  the  methods  of  analysis  and  measurement. 
When  the  character  of  the  quality  prohibits  a  strict  appli- 
cation of  measurement  for  determining  the  relative  size  of 
errors,  then  the  idea  of  measurement  should  be  utilized  by 


THE  METHOD  OF  ATTACK  383 

comparison  with  standard  samples  graded  in  such  a  way  as 
to  provide  limits. 

Using  the  Facts —  Synthesis  and  Adjustment 

The  scientific  method,  as  we  have  seen,  is  not  content 
to  stop  with  a  statement  of  facts — it  must  know  why.  In 
practical  application  this  brings  us  to  the  determination  of 
the  causes  of  variations  from  standard.  Once  the  reasons 
for  the  variations  are  known,  we  are  a  long  way  on  the  road 
to  their  correction.  Again,  it  is  a  matter  for  analysis,  for 
carefully  thorough  and  logical  reasoning,  and  for  the  use  of 
constructive  imagination  in  developing  proper  conclusions. 
For  instance,  errors  which  occur  intermittently  are  prob- 
ably due  to  the  way  in  which  processes  are  applied.  Pro- 
gressive increase  in  the  size  of  an  error  probably  indicates 
wear  or  change  in  equipment,  and  so  on. 

Skill  in  this  part  of  the  work  as  well  as  in  the  selection 
of  the  most  promising  points  of  attack  is  something  to  be 
acquired  solely  by  practice.  No  arbitrary  rule  applies  and 
the  solution  in  each  instance  will  differ  in  details,  although 
the  methods  used  are  alike  in  principle. 

After  the  problem  has  been  analyzed  and  each  small 
part  treated  separately,  the  separate  parts  must  be  put 
back  together  and  adjusted.  The  procedure  is  analysis, 
synthesis,  and  adjustment  (or  compromise),  as  already  dis- 
cussed in  several  places — notably  in  Chapter  XVI,  "Repe- 
tition Manufacturing."  Thus  the  tolerance  on  a  given 
dimension  is  a  matter  for  agreement  between  engineering, 
production,  and  inspection.  Correct  and  complete  analysis 
is  a  very  large  part  of  solving  the  problem,  because  a  de- 
tailed knowledge  of  the  truth  usually  suggests  the  cure. 
Synthesis  and  its  concomitant,  adjustment,  ordinarily  re- 
quire a  much  shorter  time  to  execute,  but  their  vital  im- 
portance cannot  be  too  strongly  stated — they  call  for  all 


384  THE  CONTROL  OF  QUALITY 

the  available  skill  and  good  judgment  which  can  be  brought 
to  bear  upon  them. 

The  Order  of  Procedure 

When  we  come  to  the  application  of  the  method  out- 
lined in  the  preceding,  it  is  very  evident  that  the  approach 
from  the  standpoint  of  quality  must  begin  with  an  intensive 
study  of  the  product  itself.  This  is  the  only  sure  and  com- 
plete way  of  taking  the  true  measure  of  an  industrial  situa- 
tion when  quality  is  to  be  the  primary  guide.  As  suggested 
in  Chapter  II  there  should  then  follow  a  similarly  careful 
study,  first,  of  the  processes  used  to  create  the  product, 
then  of  the  organization  employed  to  apply  these  processes, 
and,  finally,  of  the  system  used  to  measure  the  achieve- 
ments and  control  the  operation  of  the  organization. 

Admittedly  the  method  of  approach  which  starts  with  a 
searching  analysis  of  the  product  and  processes  may  be 
found  to  be  somewhat  arduous  and  exacting,  but  it  soon 
becomes  most  interesting  because  of  its  great  practical 
influence  on  the  enterprise.  Sometimes  minute  details  are 
considered  uninteresting,  but  as  Gilbert  K.  Chesterton 
has  remarked :  "  There  is  no  such  thing  on  earth  as  an  unin- 
teresting subject;  the  only  thing  that  can  exist  is  an  unin- 
terested person." 

Quality  is  a  variable.  Oftentimes  the  variations  are 
small,  but  it  is  the  amount  of  attention  which  is  paid  to 
just  such  little  things  that  determines  the  difference  between 
success  and  mediocrity. 

Begin  with  the  Product 

Starting  with  the  product,  the  first  step  is  to  analyze  it 
as  it  is,  and  with  reference  to  its  characteristic  qualities. 
In  what  respect  should  the  individual  articles  making  up  the 
company's  output  be  alike?  The  next  step  is  to  reduce 


THE  METHOD  OF  ATTACK  385 

these  characteristics  to  some  basis  of  measurement  for  pur- 
poses of  impersonal  comparison.  We  can  then  determine 
to  what  degree  of  likeness  it  is  sensible  to  make  the  indi- 
vidual pieces  and  establish  tolerances  and  limits  accordingly. 
This  involves  the  determining  of  how  far  the  articles  may 
be  unlike.  At  the  same  time,  and  by  the  same  means,  we 
may  observe  the  direction  which  future  improvement  of  the 
product  should  follow  toward  closer  approximation  to  the 
ideal  standard. 

Proceeding  next  to  a  study  of  the  processes  used  in 
creating  the  product,  the  investigation  takes  the  form  of 
studying  both  processes  and  product  together.  The  first 
object  sought  is  a  uniform  product  conforming  with  the 
predetermined  working  standards.  This  requires  that  the 
processes  used  to  create  the  product  must  be  controllable 
to  an  equal  uniformity.  To  bring  them  to  this  condition 
we  must  proceed  to  list  the  various  kinds  of  errors  (or  dif- 
ferences in  the  product),  their  magnitudes,  and  the  fre- 
quency with  which  each  kind  of  error  occurs.  The  next 
step  involves  listing  the  possible  and  probable  causes  of 
these  errors,  as  a  step  toward  determining  their  actual 
causes.  When  the  last-mentioned  thing  has  been  deter- 
mined, it  is  no  very  difficult  problem  in  most  cases  to  de- 
velop means  and  ways  for  reducing  the  errors — and  often 
to  eliminate  them  for  all  practical  purposes. 

If  the  solution  of  the  problem  is  not  so  easy  to  find,  then 
we  must  turn  back  to  pure  science — the  master  teacher — - 
and  develop  new  methods  from  a  fresh  start.  If  your  task 
seems  too  difficult,  it  will  reassure  you,  perhaps,  to  take  a 
look  at  the  obstacles  others  have  overcome.  One  trip 
through  a  plant  making  electric  light  bulbs,  for  example, 
is  quite  cheering.  The  winding  of  wire  filaments  too  small 
for  the  eye  to  see  the  coils  without  the  use  of  a  microscope, 
and  the  actual  use  of  the  latter  on  production  machines  is 


386 


THE  CONTROL  OF  QUALITY 


Figure  89.     Precision  Torsion  Balance — Roller-Smith 


THE  METHOD  OF  ATTACK  387 

typical;  as  also  is  the  weighing  of  these  filaments  to  a  pre- 
cision of  I  per  cent  for  weights  of  less  than  12  milligrams 
(see  Figure  89),  and  this  as  a  regular  production  proposi- 
tion. 

Written  Descriptions  of  Processes 

Presently,  as  a  result  of  this  study,  we  shall  know  how  to 
perform  each  process.  As  a  matter  of  fact,  in  work  where 
the  product  cannot  be  described  by  a  plan  (like  heat  treat- 
ing, or  weaving,  or  making  some  chemical  compound),  the 
only  method  of  description  available  is  to  build  up  an  aggre- 
gation of  explanatory  descriptions,  or  written  instructions 
for  doing  the  work.  Of  course  these  process  descriptions 
must  be  in  complete  detail,  if  they  are  to  be  of  use  either  in 
analyzing  matters  affecting  quality  or  for  use  in  instructing 
workmen.  The  creation  of  such  records  involves  learning 
your  business  in  detail,  but  that  is  a  knowledge  the  man- 
agement of  any  business  should  have  if  it  intends  to  run  the 
business,  instead  of  letting  the  business  run  the  manage- 
ment. 

There  is  one  great  distinction,  however,  that  you  can 
learn  the  technical  details  of  the  business  by  the  scientific 
method,  even  though  you  are  not  actually  able  to  do  the 
work  yourself — at  any  rate,  you  need  not  be  able  to  do  it 
as  well  as  the  man  who  is  continually  engaged  in  produc- 
tion. This  is  a  bitter  pill  to  the  extreme  type  of  "  practi- 
cal" man.  He  is  unwilling  to  disparage  the  results  of 
years  of  devotion  to  his  work — consequently  he  is  quite 
likely  to  reject  your  advice  for  improvement  by  asking  (of 
himself,  at  least),  "How  can  anyone,  who  avowedly  knows 
little  if  anything  about  this  work,  teach  me  how  to  do  it 
better?  Haven't  I  been  working  right  at  this  same  job  for 
the  last  twenty- five  years?" 

But,  as  doubtless  you  have  already  observed,  this  atti- 


388  THE  CONTROL  OF  QUALITY 

tude  fails  to  distinguish  between  knowing  the  methods  and 
principles  used  in  doing  the  work,  on  the  one  hand  (the 
why  and  how)  and  the  skill  required  for  their  execution, 
on  the  other.  One  could  write  out  the  most  particular 
instructions  for  shooting  a  rifle,  but  would  only  acquire 
the  skill  necessary  for  accurate  shooting  through  continuous 
practice.  Yet  almost  anyone  could  learn  to  shoot  by  follow- 
ing the  written  instructions  exactly. 

It  is  a  safe  statement  that  man  is  not  capable  of  doing 
anything  which  cannot  be  analyzed  by  the  scientific  method 
of  attack  and  reduced  to  a  description  written  in  clear  and 
simple  language.  Further,  such  a  description  may  be  used 
as  the  basis  for  improvement,  once  the  governing  principles 
have  been  worked  out;  and  it  can  be  employed  as  well  to 
start  any  other  intelligent  person  toward  acquiring  the  skill 
needed  in  its  execution. 

As  a  general  rule,  the  oldest  processes,  which  have  not 
yet  been  subjected  to  such  an  investigation,  are  the  most 
fertile  field  for  its  application.  There  is  no  mystery  in  any 
industrial  process,  although  it  may  well  be  that  great  skill 
is  required  for  its  proper  execution,  and  even  the  latter 
may  be  simplified. 

The  Assemblage  of  Processes 

After  the  processes  have  been  considered  in  detail,  it  is 
in  logical  order  to  consider  them  as  merely  the  principal 
working  parts  of  a  great  manufacturing  machine — the 
factory  as  a  whole.  Shop  arrangement  (especially  with  a 
view  to  care  of  material  in  process)  will  show  new  values 
for  system  and  order  in  physical  form,  as  distinguished 
from  mere  paper  systems.  Consider  the  shop  and  inspec- 
tion arrangements  with  a  view  to  planning  with  material 
and  taking  full  advantage  of  the  possibilities  of  the  principle 
of  centralized  inspection. 


THE  METHOD  OF  ATTACK  389 

Organization  and  System 

Taking  up  the  organization  next — is  it  well  balanced  as 
regards  the  main  functions  of  planning,  production,  and 
inspection?  For  this  much  is  fundamental  in  controlling 
quality.  Is  the  factory  personnel  organized  in  a  way  to 
provide  for  bringing  to  the  attention  of  the  workmen,  in 
effective  form,  the  things  they  should  know  if  quality  is  to 
be  maintained  as  it  is,  and  systematically  improved  there- 
after? Also,  does  the  organization  provide  a  competent 
person,  whose  duty  is  that  of  directing  this  improvement 
with  the  idea  of  making  progress  conscious  and  intentional  ? 

Usually  some  form  of  committee  system  will  be  found 
useful  as  a  means  of  educating  the  rank  and  file  in  the 
details  of  quality  manufacture.  It  is  well-nigh  useless  to 
spend  money  in  bringing  valuable  facts  to  light,  unless  pro- 
vision is  made  for  using  them.  Education  is  the  first  step 
toward  accomplishing  this,  and  to  be  effective,  it  should 
be  reinforced  by  methods  which  make  it  clearly  to  the  in- 
terest of  the  producer  to  put  these  lessons  into  practice. 

Finally,  some  economical  sort  of  system,  or  systems, 
should  be  devised  to  present  the  statistics  of  the  business 
(costs,  qualities,  and  quantities)  in  clear  and  useful  form 
for  the  guidance  of  the  organization  in  correcting  errors  and 
eliminating  wastes.  The  cost  system  especially  should 
locate  charges  for  damage  and  waste  against  the  responsible 
department  rather  than  against  the  department  where  they 
occur. 

In  short,  the  whole  process  of  controlling  quality  in- 
volves applying  the  scientific  method  to  the  industry,  in  a 
practical  engineering  way.  Beginning  with  an  untiring 
and  systematic  search  for  facts,  we  pass  to  a  truthful,  ac- 
curate, and  sensible  use  of  them  in  refining  our  work.  The 
method  is  an  invincible  one  for  securing  increased  output, 
at  less  expense  of  effort,  and  with  higher  quality. 


390  THE  CONTROL  OF  QUALITY 

Conclusion 

Whether  as  a  part  of  some  general  trend  for  which  the 
times  are  opportune,  or  as  the  working  out  of  economic 
laws,  or  as  a  combination  of  both  (which  is  the  most  prob- 
able), business  as  a  whole  is  working  toward  greater  truth 
and  fidelity  to  accuracy.  This  increasing  tendency  toward 
exact  definition,  which  is  the  precursor  of  improved  and 
better  regulated  quality,  has  shown  itself  rather  promi- 
nently at  times.  Some  years  ago,  for  example,  there  began 
a  great  movement  for  "pure  food."  More  recently,  similar 
action  has  been  taken  for  pure  advertising,  and  one  form  of 
truthfulness  which  the  latter  has  urged  is  the  frank  and 
open  publication  of  technical  details.  Things  are  being 
called  what  they  really  are,  and  the  proof  supplied,  instead 
of  making  mere  assertions  about  quality  and  performance. 

This  situation  is  encouraging,  especially  if  you  are  one 
of  those  who  believe  that  the  business  of  the  future  will  be 
built  upon  a  sounder  basis  of  merit,  service,  and  worth, 
than  ever  before.  If  this  is  a  correct  viewpoint,  then  is 
not  the  control  of  quality  the  first  step  in  that  direction? 
Surely  it  is  the  basis  for  both  service  and  the  profit  which 
follows  real  service.  American  industry  has  been  famous 
for  quantity  production.  Why  should  it  not  be  distin- 
guished also  for  qualities  that  are  definite  and  certain? 
When  capitalists  and  industrial  executives  regard  quality 
in  this  light,  the  biggest  step  toward  the  qualitative  im- 
provement of  industry  will  have  been  taken,  because  there 
is  no  serious  difficulty  in  the  way  of  its  achievement. 

Very  happily,  quality  is  like  many  other  things  which 
you  can  have  if  you  only  want  them  badly  enough.  In  his 
essay  on  "The  Art  of  Seeing  Things,"  John  Burroughs  says 
that  the  secret  of  the  successful  angler's  effort  is  no  doubt 
due  to  love  of  the  sport.  "What  we  love  to  do,  that  we  do 
well."  Without  the  strong  desire  for  quality,  beginning  at 


THE  METHOD  OF  ATTACK  391 

the  very  top  of  the  organization,  there  is  little  chance  for 
securing  quality.  Thus  it  is  one  of  the  prime  responsibili- 
ties of  ownership  and  management. 

There  is  no  danger,  either,  in  setting  our  ideal  standards 
too  high,  because  the  fact  that  the  realized  standards  are 
lower  need  not  be  discouraging.  For  it  does  not  prevent 
the  ideal  from  serving  a  most  useful  purpose,  by  indicating 
the  direction  improvement  should  take.  "Ideals"-  -  said 
Carl  Schurz — "are  like  stars.  You  cannot  touch  them 
with  your  hands  but  like  the  seafaring  man  on  the  desert  of 
waters  you  choose  them  as  your  guides  and,  following 
them,  you  reach  your  destiny." 

Granted  that  quality  is  a  desirable  thing  to  have,  the 
way  to  approach  the  task  of  placing  it  under  sure  control 
is  the  simple  one  of  seeking  true  facts  and  being  guided 
thereby,  in  accordance  with  a  definite  campaign.  In  the 
main,  the  methods  most  useful  in  the  control  of  quality  are 
merely  the  old-fashioned,  time-honored  ways  of  engineering 
with  perhaps  a  little  different  slant.  "Engineering  is  the 
art  of  organizing  and  directing  men,  and  of  controlling  the 
forces  and  materials  of  nature  for  the  benefit  of  the  human 
race."  There  is  nothing  especially  dramatic  or  mysterious 
about  engineering  methods,  but  the  results  of  their  intelli- 
gent and  earnest  application  are  pure  magic.  They  present 
the  most  romantic  possibilities  for  solving  the  problems  of 
the  world  that  confronts  man  in  his  upward  climb. 


INDEX 


Accuracy,  (See  "Errors,"  "Measure- 
ment," "Precision") 
Adjustable  limit  gages,  307 

Illustrations,  222,  235,  307,  308 
Aisle  arrangements,  for  central  inspec- 
tion system,  132 
Chart,  133 

Alford,  L.  P.,  quoted,  14 
Allowance, 

defined,  254,  255 

precautions   in    working   from,    to 

determine  tolerances,  255-258 
American  amplifying  gage,  298 
American  International  Corp., 

inspection  form,  80 
American  Locomotive  Co., 

Illustrations,  18,  51,  96,  183,  192- 

196,  198,  199,  202 

quality  control  in  war  work,  188- 
202 

bullet  manufacture,  197 
inspection,  201 

Illustrations,  51,  183 
shell  manufacture,  188-197 

Illustrations,  192-196 
time  fuse  manufacture,  200 
Illustrations,  18,  198,  199 
Appearance, 

relation  of  color  to,  347 
standards  of,  367 
Armstrong  Cork  Co., 

experience  with  quality  bonus,  21, 

23 
Assembling, 

department,  inspection's  aid  to,  79- 
83 
example  of  selective  assembly,  82 


Assembling — Continued, 

repetition  manufacturing,  economy 

in,  269 

standards,  261 
Automobile  industry, 

example  of  highly  developed  form 

of  inspection,  174-180 
at  Packard  Motor  Car  Co.,  174- 
177  (See  also  "Packard  Motor 
Car  Co.") 

former  practice,  178-180 
degree   of   precision,    obtained    in, 
331-333 

B 

Bench  inspection,  164 
Bench  inspectors,  qualifications,  152 
Block  gages,  (See  "Johansson  block 
gages,""  Pratt  &  Whitney  gages") 
Bonus,  quality  (See  "Quality  bonus") 
Brightness,  a  color  constant,  355 
Brown  and  Sharpe  Co., 
gages, 

Illustration,  305 
measuring  machine,  287 

Illustration,  288 

micrometer  calipers,  proper  method 
of  using, 

Illustrations,  28,  31,  218,  253, 

257,  260 

Bulletin   boards,   suggestion   for  im- 
provements in,  90 
Bulletins,  department,  158 
Bureau  of  Standards,  215,  216,  350 


Carnegie,  Andrew,  quoted  in  "Auto- 
biography," 17 


393 


394 


INDEX 


Central  inspection,  49-52,  115-138 
advantages,  137,  138 
arrangement  of  shop,  123 

adaptation   to   high-grade   close 

work,  131-134 
adaptation  to  rough  work,  129- 

130 

line  of  flow  of  work  first  step  in, 
123 

Chart,  123 
several  spaces,  134 
at  Lincoln  Motor  Co., 
at  Packard  Motor  Car  Co.,  175 

Illustration,  37 
cribs     (See     "Central     inspection 

cribs") 
forms  of,  115 

self-counting  trays,  116-122 

Illustrations,  118,  119,  120,  121 
two-bin  system,  122 
most    highly    specialized    form    of 

inspection,  115 
standard,  desirable,  135 
Central  inspection  cribs, 

Illustration,  126 

arrangement    of    material    storage 
point  in,  137 

Illustration,  137 
construction,  125 

Illustration,  127 
floor  plan,  128,  129 

aisle  arrangements,  132-134 

Charts,  128,  129,  132,  133,  135 
layout,  124 

Charts,  124,  125 
Charles-William     Stores,     inspection 

methods,  186 

Chief  inspector,  (See  also  "  Inspection 
department,    management    of") 
bulletins  issued  by,  158 
location  of  office,  156 
organization  of  work,  144 

Chart,  145 
qualifications,  140-142 


Chief  inspector — Continued, 
relation  to  organization, 

at  Packard  Motor  Car  Co.,  174 

at  Pratt  and  Whitney  Co.,  181 
staff, 

duties  of,  148-151 

subordinates,  144 

understudies,  146 
titles,  143 

use  of  conferences,  157 
Church,  A.  Hamilton,  quoted,  14 
Clearance,  defined,  255 
Color,  346-367 

analysis  of,  methods,  359 

instruments,  361  (See  also  sub- 
heading "measuring  instru- 
ments" below) 

monochromatic  filters,  360 

prisms,  359 
appearance  and,  347 
as  light,  factors  of,  351-355 

eye,  the,  355 

illuminant,  the,  351-353 

subject,  the,  354 
constants,  355 

brightness,  356 

hue,  355 

purity,  356 
control  by  standard  samples,  348 

atlas  of  colors,  349 

color  card,  213,  348-349 

dangers  of,  350 

errors  in  work,  reduction  of,  366 
measurement  of,  213 
measuring  instruments,  361,  365 

monochromatic  colorimeter,  363 

spectrophotometer,  362 

Diagram,  363 
tints  and  shades,  357 
tone,  355 
vision,  358 
Comparators,  298 
Hartness,  323 

Illustrations,  324,  325 


INDEX 


395 


Conditioning  of  material,  standards, 

250 

Conferences,  use  of,  by  chief  inspec- 
tor, 157 
Continuous  processing, 

importance  of  uniformity  in,  275 
Continuous  product, 

practice  in  regard  to  inspection  of 

manufacture  of,  184 
Costs, 

decreased  by, 

quality  control,  15-19 
repetition    manufacturing,    264- 
.    280 
selling,  24 


Defects,  remedy  of,  combined  with 

inspection,  53 
Design,  the,  237 
changes  in, 

avoid  if  possible,  242,  245 
improvement,  243 
progress  towards  more  exact,  240 
Dimension,    (See  also   "Dimensional 
control  laboratory,"   "Measure- 
ment") 

working  standards,  252-254,  258- 
261 

basis  of  repetition  work,  252 
definitions  for,  254,  255 
Dimensional  control  laboratory,  281- 

302 
material  equipment, 

Brown    and    Sharpe    measuring 
machine,  287 
Illustration,  288 
comparators,  298 
Johansson  block  gages,  294-297 

Illustration,  297 
miscellaneous,  300 
Pratt    and    Whitney    measuring 
machine,  289-293 
Illustrations,  290,  292 


Dimensional     control     laboratory — 

Continued, 

Pratt    and    Whitney     precision 
gages,  298 

surface  plate,  285 
physical  conditions, 

cleanliness,  284 

floor  coverings,  284 

furnishings,  285 

humidity,  284 

lighting,  284 

noise,  284 

temperature,  283 

vibration,  284 
Dispatching,    relation    of    inspection 

to,  113 
Duplicate  manufacturing,  277 

E 

Elgin  National  Watch  Co., 

ratio  of  inspectors  to  workers,  182 
Employees, 

dimensional  control  laboratory, 
301 

discovering  native  ability  among, 

153-155 

effect  of  inspection  data  on, 
reduction  of  fatigue,  93 
stimulus  to  interest,  90,  91 

inspection  force  (See  "Inspection 
department,  management  of" 
and  "organization  of") 

number  of,  relation  between  out- 
put and,  162 
Engineering  department,  64 

relation  to  inspection,  72 
Engineer,    the,    as    co-ordinator    of 

science  and  industry,  376 
Errors, 

in  color  work,  366 

in  measuring,  232 
classes  of,  227 
cure  for,  231 


396 


INDEX 


Errors — Continued, 

frequency  of  occurrence,  228 

Chart,  228 
reasons  for  accumulation  of,  226- 

232 
Eye,  the,  as  a  factor  in  color,  351 


Gages — Continued, 
special,  310 
standard,  defined,  313 
thread-gaging,    (See   "Thread-gag- 
ing") 
tolerances,  311 


Finish, 

effect  on  accuracy,  344 

standards,  251-252 
First-piece  inspection,  59-61 
Fits,  (See  "Precision") 
Fixed-dimension  limit  gages,  304 
Floor-inspection,  52 

at  Packard  Motor  Car  Co.,  175 

qualifications  of  inspectors,  152 
Flow  of  work  in  process,  (See  "Work 

in  process") 

Foundries,     practice    in     regard     to 
inspection,  184 


Gages,  303-316  (See  also  "Measuring 

instruments") 
adjustable  limit,  307 

Illustrations,  222,  235,  307,  308 
application  of,  311 
checking,  312,  313 

Illustration,  48,  282 
constitute  working  standards,  259 
fixed-dimension  limit,  304 
fluid,  298 

Illustration,  167 
master,  defined,  313 
micrometer  calipers,  proper  method 
of  using, 

Illustrations,  28,  31,  218,  253, 

257,  260 
multiplying,  309 

types,  310 

reference,  defined,  313 
shop  or  working,  defined,  313 
slip  in  transferring  size,  314 


Hartness  comparator,  323 
Illustrations,  324,  325 
Hartness,  James,  quoted,  318-319 
Hoover,  Herbert,  quoted,  94 
Hue,  a  color  constant,  355 

I 

Illuminant,  the,  a  factor  in  color,  351- 

353 

Industrial    management,    costs    (See 
"Costs") 

employees  (See  "Employees") 

engineering  department,  64 
relation  to  inspection,  72 

inspection,  (See  also  "Inspection") 
purpose,  help,  69 
recognition  of  importance  of,  63 
relation   of   to   engineering   and 
production,  68 

inspection  department,  67  (See  also 
"Inspection  department") 

organization  parallel  with  govern- 
mental, 67 

planning  (See  "Planning") 

problems,    advantages    of    quality 

control, 

costs  decreased,  15-19,  24 
labor     relationships     improved, 

12-15 
output  increased,  15-19 

production  department,  66 
relation  to  inspection,  72 

quality  a  prime  responsibility  of, 

391 

real  vs.  apparent  organization,  70 
Industrial  revolution,  the,  266 


INDEX 


397 


Inspection, 

American  Locomotive  Co.,  war- 
time work,  201 

amount  necessary,  54-57 

automobile  plants,  example  of 
highly  developed  form  of,  173- 
180 

at  Packard  Motor  Car  Co.,  174- 
177 

Chart,  174 
former  practice,  178-180 

bench,  164 

central  (See  "Central  inspection") 

continuous  processing,  185 

continuous  product,  184 

contribution  of  to  general  service, 

74-94 

arrangement,  care,  and  analysis 

of  work  in  process,  83 
collection  of  useful  information, 

74 

handling  rejected  parts,  85-89 
in  assembling   department,    79- 

83 

provides  production  data,  89 

reduction  of  fatigue,  93 

stimulus  to  interest  of  individual 
workers,  90,  91 

trouble  reports,  75-78 

Forms,  76,  80 
cost,  relation  between  output  and 

size  of  inspection  force,  163 
cribs     (See     "Central     inspection 

cribs") 
denned, 36 

relation  to  quality  and  quality 

control,  36 

department    (See   "Inspection   de- 
partment") 
economies  in,  61 
elimination  of  unnecessary,  57 
evolution  of,  39 
extensive,  when  desirable,  173 

automobile  factories,  174 


I  nspection — Continued, 

machine  tool  manufacture,  181 
small  precision  work,  182 

first-piece,  59-61 

floor,  52 

at    Packard     Motor    Car    Co., 

175 

qualifications  of  inspectors,   152 
force  (See  "Inspection  department, 

management  of,"  and  "organiza- 
tion of") 
foundries,  184 
gear,  Lincoln  Motor  Co., 

Illustration,  88 
general  machine  shop,  184 
individual    piece,     final,     Packard 

Motor  Car  Co.,  175 
machine  tool  manufacture,  181 

relation  of  inspection  department 

to  organization,  181 
mail  order  houses,  186 
necessity  for,  35-45 
operating,   on  finished  vehicles  at 

Packard  Motor  Car  Co.,  177 
relation  to, 

engineering  and   production,   68 

planning,  (See  "Planning") 
rough  stock,  Packard    Motor  Car 

Co., 

Illustration,  58 
sampling,  59-61 
small  precision  work,  182 
tool  and  gage,  Packard  Motor  Car 

Co., 

Illustration,  42 
types  of,  46-53 

governed  by  special  factory  situa- 
tion, 46 

loosely  organized,  184 

office,  47 

raw  materials,  46 

tool,  49 

work   in    process,    49    (See   also 
"  Work  in  process,  inspection  ") 


398 


INDEX 


Inspection     department,     (See     also 

"Industrial  management") 
importance  of,   recognition   of  by 

management,  63 
management  of,  156-171 
bulletins,  158 
conferences,  157 
co-ordination  of  work,  156 
instruction  of  inspectors,  164-166 
female  labor,  166-170 
location     of     chief     inspector's 

office,  156 

morale,  value  of  high,  170 
overtime,  162 
permanent  personnel,  desirability 

of,  159 

piece  work,  161 
promotion  of  employees,  159 
proportion  of  output  to  size  of 

force,  163 

Chart,  163 
task,  156 
wages  of,  1 60 
working  hours,  162 
organization  of,  139-155 

basis,    amount    of    work    to    be 

done,  142 

bench  inspector,  152 
chief    inspector,     140-142     (See 

also  "Chief  inspector") 
combination   of   line    and    staff, 

144 

Chart,  145 
development  of,  139 
floor-inspectors,  152 
inspectors,  147-151 
personnel,     discovering      native 

ability  among,  152-154 
personnel  qualifications  of,  151 
ratio   of    inspectors   to   workers 

(See  "Ratio  of  inspectors  to 

workers") 
related  work,  142 
staff  duties,  147-151 


I  nspection  department — Continued, 
understudies  to  chief  inspector, 

146 

purpose,  69 
relation  to  organization, 

engineering  and  production  de- 
partments, 64-69,  72 
in    machine    tool    manufacture, 
181 

Inspectors  (See  "Chief  inspector," 
"Inspection  department,  man- 
agement of"  and  "organization 
of") 

Instruments,  measuring  (See  "Meas- 
uring instruments") 
Interchangeable  manufacturing,  265, 
272     (See  also  "Repetition  man- 
ufacturing") 


Johansson,  C.  E.,  295 
Johansson  block  gages,  294 

Illustrations,  n,  222,  235,  239, 
241,  268,  273,  276,  297,  299 
remarkable  accuracy  of,  296 
secrecy  of  manufacture,  297 
Jones  and  Lamson  Machine  Co., 
Illustrations,  320,  324,  326 


Labor  (See  "Employees") 
Labor  relationships, 

improved  by  quality  control,  12-15 
Lassiter,  C.  K.,  quoted,  201 
Law  of  chance,  228 

Chart,  228 

Lewis,  Huber  B.,  quoted,  314-316 
Liberty  motors,  example  of  successful 

quality  control,  203-206 
Light,  color  as  (See  "Color") 
Limits, 

defined,  254, 255 

precautions    in    determining    from 
allowance,  255-258 


INDEX 


399 


Lincoln  Motor  Co., 

Illustrations,  37,  48,  71,  88,  204, 

205,  282 
central  inspection  in, 

Illustration,  37 
quality  control  in  war  work,  203-206 

Forms,  204,  205 
Luckiesch,  M.,  quoted,  355,  371 

M 

Machine  shops,  general, 

practice  in  regard  to  inspection,  184 
Machine  tool  manufacture, 

by    interchangeable    manufacture, 

278 
example  of  highly  developed  form 

of  inspection,  181 
relation  of  inspection  department 

to  organization,  181 
Mail  order  house, 

inspection     methods    at    Charles- 
William  Stores,  1 86 
Management  (See  "Industrial  man- 
agement") 
Manufacturing, 

and  art,  difference,  264 
economies     in     (See     "  Repetition 

manufacturing  ") 

repetition,  264-280  (See  also  "  Rep- 
etition manufacturing") 
schedule,    basis    of    space    assign- 
ments, 109 

Master  control  sheet,  101 
Master  gage,  denned,  313 
Material  in  process, 

necessity    for    continuous    supply 

of,  99 

space  assignments  for,  in 
two-bin  system  of  storage,  122 
Measurement,     210-232     (See     also 
"Dimension,"         "Dimensional 
control  laboratory") 
absolute  accuracy  impossible,  234 
denned, 234 


Measurement — Continued, 
errors  in, 

accumulation  of,  229-231 

classes  of,  227 

cure  for,  231 

frequency  of  occurrence,  228 

Chart,  228 
theory  of,  226 
evolution  of,  210-222 

comparison    with    graded    scale, 

214 
instruments,   217-222    (See  also 

"Measuring  instruments") 
selection  of  qualities  for,  211,212 
standard  samples,  212 
foundation  of  exact  sciences,  210 
instruments   (See   "Measuring  in- 
struments") 
precision    in,    223-225     (See    also 

"Precision") 
starting  point  of   quality   control, 

210 

units  of,  choice  of,  217 
Measuring     instruments     (See     also 
"Dimensional     control     labora- 
tory,"    "Gages,"      "Measuring 
machines") 
choice  of,  222 
color,  361,  365 

monochromatic  colorimeter,  363 
spectrophotometer,  362 

Diagram,  303 
comparators,  298,  323 

Illustrations,  324,  325 
danger  of  overgraduation,  220 
precision,  223-225 
requirements,  219 
Measuring  machines, 
Brown  and  Sharpe,  287 

Illustration,  288 
Pratt  and  Whitney,  289 

Illustrations,  290,  292 
Mechanical  devices,  inspection  by,  53 
Mechanical  revolution,  the,  267 


400 


INDEX 


Micrometer  calipers, 
proper  method  of  using, 

Illustrations,  28,  31,  218,  253, 

257,  260 
Monochromatic       colorimeter,       for 

measuring  color,  363 
Monochromatic   filters,    use   in   ana- 
lyzing color,  350 
Multiplying  gages,  309 
types,  310 

N 

North,  Simeon,  early  exponent  of 
interchangeable  manufacturing, 
270 

O 

Office  inspection,  47 

Operation  data  sheet,  104 
Form,  100-107 

Operation  study  sheet,  104 
Form,  105 

Operation  symbols,  102-104 

Organization  (See  "Industrial  man- 
agement") 

Output,  increased  by  quality  control, 
15-19 

Overgraduation  of  instruments, 
danger  of,  220 

Overtime,  inspection  force,  162 


Packard  Motor  Car  Co., 

Illustrations,  42,  58,  65,  167,  174, 

176,  179 
inspection, 

example    of    highly    developed 

form  of,  174 
organization,  174-177 

Chart,  174 
tool  and  gage, 

Illustration,  42 

Personnel  (See  "Employees") 
Piece  work, 

in  inspection  department,  161 


Piece  work — Continued, 

interfered  with  by  uneven  flow  of 

work  in  process,  98 
Planning,  95-114 

dispatching,  relation  of  inspection 

to,  113 

manufacturing  schedule,  109 
master,  101 

master  control  sheet,  101 
materials  in  process, 

necessity  for  continuous  supply, 

99 

space  assignments,  1 1 1 
operation  data  sheet,  104 

Form,  106-107 
operation  study  sheet,  104 

Form,  105 

operation  symbols,  102-104 
raw   materials,   necessity   for  con- 
tinuous supply,  98 
route  tags,  108 

Form,  108 
work  in  process, 

allowance  for  losses  in,  109 
determining  quantities,  1 10 
disadvantages  of  uneven  flow, 

97,  98 
flow  of,  95 

Planning    department    (See    "Plan- 
ning") 

Polakov,  W.  N.,  quoted,  15 
Pratt  and  Whitney  Co., 
gages, 

Illustrations,    150,    307,    308, 

315,  322,  323 
adjustable  limit, 
precision,  298 
taper,  315 
thread, 

measuring  machine,  289 
Illustrations,  290,  292 
relation  of  inspection  department 
to  organization,  181 


INDEX 


401 


Precision     (See    also     "Dimensional 

control  laboratory") 
advantages  of,  281 
depends  on   service   requirements, 

,328  . 
dimensional,  330-345 

automobile  experience,  331-333 
checks,  quick,  345 
degree  practicable,  330 
effect  of  finish  on,  344 
obtaining,  precautions  in,  341 
tables  of  tolerances  and  limits, 

333-34° 

Illustrations,  334-338 
gages,  Pratt  and  Whitney,  298 
in  manufacture  of  small  high-grade 

articles,  182 
in  measuring,  223,  224 
in  workmanship,  225 
instruments,  handling,  165 
torsion  balance, 

Illustration,  386 

Prestometer  or  Prestwich  fluid  gage, 
298 

Illustration,  167 
Prism,  use  in  analyzing  color, 

Illustration,  359 
Product, 

study  of,  starting  point  of  qual- 
ity control,  (See  "Quality  con- 
trol") 

Production  department,  66 
relation  to  inspection,  72 
Purity,  a  color  constant,  356 
reducing,  makes  tints,  357 


Quality  (See  also  "Quality  control") 
a  prime  responsibility  of  manage- 
ment, 391 
defined,  4,  233-247 
essence  of,  5 

incentive  to  increased  production, 
91 


Quality — Continued, 

inspection  the  instrument  for  meas- 
uring (See  "Inspection") 

records,  382 

standardization     alone     does     not 
bring,  5 

standards  (See  "Standards") 

variability  of,  235 

vs.  quantity,  3,  19,  235 
Quality  bonus,  20 

Armstrong  Cork  Co.'s  experience, 
21,  23 

The    Shelton    Loom's    experience, 

21 

Quality  control    (See  also   "Inspec- 
tion") 

advantages     of,     in     management 

problems, 

costs  decreased,  15-19 
labor     relationships     improved, 

12-15 

output  increased,  15-19 
selling  expense  decreased,  24 

color  (See  "Color  control") 

complexity  of  problem  of,  187 

dimensional     (See     "Dimensional 
control  laboratory") 

failure,  instances  of,  9 

measurement,  relation  of  to,  210- 
232  (See  also  "Measurement") 

method  of  attack,  377-391 
analysis  of  facts,  379,  380 
beginning  with  the  product,  384 
getting  the  facts,  378 
order  of  procedure,  384 
organization  and  system,  389 
quality  records,  382 
study  of  processes,  385-388 
synthesis   and   adjustment,    383 

root  of  production  economy,  279 

study  of  processes  of  making  prod- 
uct, second  step  in,  385 
assemblage  of,  388 
written  descriptions  of,  387 


402 


INDEX 


Quality  control — Continued, 

study  of  product,   starting  point, 

25,  236,  384 

consumer  requirements,  26 
design,  26-30,  236 
need  of  inspection,  33 
operating  organization  and  rec- 
ords, 32 
processes,  31 
raw  materials,  30 
workmanship,  32 

war  time  success  in,   examples  of 
188-209 
American  Locomotive  Co.,  188- 

202 

Lincoln  Motor  Co.,  203-206 
Remington  Arms  Co.,  206-208 
Quantity, 

vs.  quality,  3,  19 

R 

Ratio  of  inspectors  to  workers,  186 
American  Locomotive  Co.,  201 
General  machine  shops  and  found- 
ries, 184 

machine  tool  industry,  181 
Packard  Motor  Car  Co.,  177-178 
small  precision  work,  182 
Wahl  Co.,  141 
Raw  material, 

importance    of    uniformity    of,    in 

repetition  manufacturing,  273 
inspection,  46 
necessity  for  continuous  supply  of, 

98 

standards,  249 
Reference  gage,  defined,  313 
Rejected  parts, 
handling  of,  85-89 

at     Packard     Motor     Car     Co., 
176 

Form,  176 

percentage  of,   American  Locomo- 
tive Co.  war  work,  201 


Remington  Arms  Co., 

Forms    and    Illustrations,    105, 

108,  126,  246 

quality  control  in,  206-208 
Repetition    manufacturing,    264-280 
basis  of,  establishment  of  working 

standards,  252 
economy  in, 
assembling,  269 
labor,  267,  269 
development  of, 

industrial  revolution,  266 
mechanical  revolution,  267 
duplicate  manufacturing,  277 
.     interchangeable   manufacture,   one 

class  of,  265,  271 
machine  tool  production,  278 
partial  interchangeability,  277 
precautions  in  working  from  allow- 
ances to  determination  of  toler- 
ances and  limits,  255-258 
purpose,    economy    of    production 

uniformity, 

at  all  stages  essential,  265 
basis  of,  264 

in  continuous  processing,  275 
in  raw  materials,  273 
work    of    Simeon    North    and    Eli 

Whitney,  270 

Roller-Smith    Co.,    precision    torsion 
balance, 

Illustration,  386 
Route  tags,  108 
Form,  1 08 


Samples,  standard, 
color,  348 
atlas  of,  349 
card,  348-349 
dangers  of,  350 
selection  of,  in  measurement,  212, 

213 
dangers  in,  214 


INDEX 


403 


Sampling,  in  inspection,  59-61,  164 
Scientific  attitude  of  mind,  368-376 
Self-counting  trays, 

use  in  central  inspection,  116-122 
Selling  expense, 

decreased  by  quality  control,  24 
Shell  manufacture, 

American    Locomotive    Co.,    188- 

197 

Shelton  Looms,  The 
Illustration,  185 
experience  with  quality  bonus,  21 

Illustration,  22 

Shop  arrangement  (See  "Central  in- 
spection, arrangement  of  shop") 
Shop  gage,  denned,  313 
S.  K.  F.  Ball  Bearing  Co.,  proportion 

of  inspectors,  141 

Spectrophotometer,      for      analyzing 
color,  362 

Diagram,  363 
Spectrum,    use    in    analyzing    color, 

359 

Illustration,  359 
Springfield-Enfield   Rifle  production, 

quality  control  in,  206-208 
Stanbrough,  D.  G.,  quoted,  331-333 
Standard  gage,  defined,  313 
Standardization, 

quality  not  secured  by  alone,  5 
Standards, 

appearance,  367 
ideal,  233-247 

attainment  of,  difficult,  240 
defined,  239 

the  design,  236-237,  239-247 
variations  from,  235 
manufacturing,  236 
measuring, 

development  of,  210 

for  United  States,  215,  216 

graded   scale,   comparison   with, 

215 
samples,  212-214 


Standards — Continued, 

necessary  in  order  to  state  a  quality, 

233 

theoretical  or  100  per  cent,  237,  238 
uniform, 

basis  of  repetition  manufacture, 
279 

securing,  7 
working, 

allowable  variations  from,   254, 

255 

assembling,  261 

conditioning  of  material,  250 

determination  of,  248 

dimension    and    form,    252-254, 
258,  261 

finish,  251 

gages  control,  when  used,  259 

precautions,  255-258 

raw  material,  249-250 

tests,  262 
Surface  plate, 

in  dimensional  control  laboratory, 

285 
Swedish  block  gages  (See  "Johansson 

block  gages") 

Sweet,  John  E.,  quoted,  238,  344 
Symbolization,  102-104 


Taylor,  Dr.  Frederick  W.,  theory  of, 

regarding  inspection,  64 
Thompson,  Gen.  John  T.,  quoted,  207 
Thread-gaging, 

equipment,  326,  327 

Hartness  comparator,  323 

Illustrations,  324,  325 
working  gages,  322 
evolution  of,  317 
interrelation  of  elements,  319 
precision    depends    on    service    re- 
quirements, 328 
purpose  of,  318 
tolerances,  327 


404 


INDEX 


Time  fuse  manufacture, 
American  Locomotive  Co., 

Forms  and    Illustrations,    18, 

198,  199 
Tingley,   Edward    H.,    quoted,    117- 

122 

Tolerance, 

denned,  254,  255 

gages,  311 

precautions    in    determining    from 

allowance,  255-258 
tables  of,  333~34° 

Illustrations,  334-338 
thread  gage,  327 
Tool  inspection,  49 
Trouble  reports,  75-78 

Forms,  76,  80 
Turnover, 

inspection    department    personnel, 

158 

Two-bin  system  of  storage  for  mate- 
rial in  process,  122 


U 


Units  of  measurement,  choice  of,  217 

W 
Wages, 

inspection  force,  160 

piece  work  system,  161 
Wahl  Co.,  proportion  of  inspectors, 
141 


War  work,  quality  control  in,  (See 
"Quality  control,  war  time  suc- 
cess in") 

Wells,  Frank  O.,  quoted,  306,  327,  328 
\Veston  Electrical  Instrument  Co., 

inspection  organization,  182 
W'hitney,  Eli,  early  exponent  of  inter- 
changeable manufacturing,  270 
Wolf,  Robert  B.,  quoted,  14 
Women  as  inspectors,  166-170 
Work  in  flow  (See  "  WTork  in  process") 
Work  in  process, 
analysis  of,  85 
arrangement  of,  83,  84 
determining  quantities  of,  no 
flow  of,  95 

Illustration,  96 

disadvantages  of  uneven,  97,  98 
line   of,    first   step   in   arranging 
shop,  123 
Chart,  123 
inspection,  49 

by  special  mechanical  devices,  53 

centralized,  49-52 

combined  with  remedy  of  defects, 

53 

floor,  52 

losses  in,  allowance  for,  109 
Working  hours   inspection  force,  162 
Working  standards  (See  "Standards, 

working") 

Working  or  workman's  gage,  defined, 
313 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


AN  INITIAL  FINE  OF  25  CENTS 

WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $1.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


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YC  24257 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


